Filter system having individually separable filter chambers

Abstract

A device for providing a process gas atmosphere during a manufacturing method for a three-dimensional object (2) in a process chamber (3) of an additive manufacturing device comprises a gas circulation system with a gas circuit for a process gas conducted through a process chamber (3), the gas circuit being closed during operation, wherein a filter system (40) having a plurality of filter chambers (41a, 41b, 41c) is disposed in the closed gas circuit, at least three filter chambers are provided, 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) for controlling the gas circuit is provided, the gas control device being designed such that it can separate a number of filter chambers (41a, 41b, 41c) from the gas circuit during the manufacturing method in progress and at the same time can ensure that, at least for part of the time, preferably constantly, the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit.

Description

[0001] Filter system with individually separable filter chambers

[0002] The present invention relates to a device and a method for providing a process gas atmosphere during an additive manufacturing process, as well as to an additive manufacturing process and an additive manufacturing device adapted thereto.

[0003] Devices and methods for the additive production of three-dimensional objects are used, for example, in processes known as "rapid prototyping," "rapid tooling," and "additive manufacturing." One example of such a process is known as "selective laser sintering" or "selective laser melting." In this process, a layer of a generally powdered build material is repeatedly applied, and the build material is selectively solidified in each layer by selectively irradiating locations corresponding to the cross-section of the object to be manufactured in this layer with a laser beam. For example, by partially or completely melting the build material at these locations using the energy provided by the laser beam, and the melt subsequently solidifies upon cooling. Further details are described, for example, in EP 2 978 589 B1.During an additive manufacturing process, a process gas atmosphere is often maintained in a process chamber where the build material is selectively treated with radiation. This process gas atmosphere is typically an inert gas atmosphere (also referred to as a "protective gas atmosphere"), as some build materials, especially those containing metals, tend to oxidize at the high temperatures encountered. This would prevent the formation of objects or at least prevent the formation of objects with the desired material structure. For example, titanium could begin to burn uncontrollably in the presence of oxygen.

[0004] During the manufacturing process, irradiation often causes a portion of the build material to evaporate, resulting in the formation of condensate after the resulting vapors resolidify. Furthermore, a portion of the build material is often disturbed. Furthermore, irradiation can cause spatter. These are usually solidified droplets of the melt of the build material with a diameter between 20 and 300 pm, for example. Spatter is ejected from the resulting melt or melt pool, for example, when the laser beam penetrates.

[0005] The aforementioned effects during irradiation of the build material also lead to impurities in the process gas atmosphere, which can negatively influence the additive manufacturing process, in particular can reduce the quality of the manufactured objects. For example, a laser beam scanning the build material can be absorbed, scattered or deflected by impurities contained in the process gas atmosphere. Furthermore, impurities can also precipitate on a coupling window for the laser beam or deposit on the surface of a build material layer. In order to meet the high quality and efficiency requirements of the manufacturing process, such impurities must therefore be removed from the process chamber as quickly as possible. For this purpose, a gas flow is usually generated in the process chamber. To keep resource consumption low, the process gas, e.g. argon, is circulated.However, this requires the process gas to be filtered to remove impurities before being fed back into the process chamber. For this purpose, a filter device with a suitable filter element is installed in the process gas circuit. Since the filter elements used become increasingly contaminated over the course of operation, they must be exchanged or replaced at regular intervals. To do this, the process gas circuit is interrupted and the filter element removed. After a new filter element is inserted, the process gas circuit is then restarted.

[0006] In order to further reduce resource consumption, DE 102014 207 160 A1 proposes to carry out a cyclic cleaning of a filter element by means of a gas pressure pulse in order to extend the replacement interval of the filter element.

[0007] EP 3 321 071 A1 addresses the problem that the operation of an additive manufacturing device must be interrupted when the filter element is replaced, since an additive manufacturing process can only be carried out if the process gas flow is filtered. To solve this problem, a switching device is proposed by means of which several filter modules can be individually switched into an operating state in which they are permeable to process gas and into a non-operating state in which they are not permeable to process gas. This ensures that the operation of the additive manufacturing device does not have to be interrupted during the replacement of a filter element.

[0008] The inventors have discovered that cleaning and replacing filter elements can lead to offsets and discolorations in the manufactured objects, which impair the quality.

[0009] It is therefore an object of the invention to provide a device and a method by means of which the quality of the manufactured objects can be improved. This object is achieved by a device and a method for providing a process gas atmosphere according to claims 1 and 14, as well as by an additive manufacturing device and an additive manufacturing method according to claims 13 and 20. Further developments of the invention are specified in the dependent claims. The methods can also be further developed by the features of the devices recited in the description or the dependent device claims. Likewise, the devices can also be further developed by the features of the methods recited in the description or the dependent method claims.

[0010] A device according to the invention for providing a process gas atmosphere during a manufacturing process of a three-dimensional object in a process chamber of an additive manufacturing device, in which the object is manufactured by applying a build-up material layer upon layer and solidifying the build-up material by supplying radiation energy to solidification points in each layer associated with the cross-section of the object in this layer, which device comprises a gas circulation system with a gas circuit that is closed during operation for a process gas conducted through the process chamber, wherein a filter system with a plurality of filter chambers is arranged in the closed gas circuit, is characterized in that at least three filter chambers are present, each of which has at least one filter element for filtering particles in the gas circuit, and a gas control device is present for controlling the gas circuit,which is designed in such a way that it can separate a number of filter chambers from the gas circuit during the ongoing manufacturing process and can ensure that at least temporarily, preferably permanently, a number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit.

[0011] Additive manufacturing devices to which the invention relates are, in particular, those suitable for the generative production of three-dimensional objects, in particular from a metal-containing construction material. This particularly applies to manufacturing devices in which the objects are built up layer by layer, for example laser melting and laser sintering devices. For supplying the radiation energy, one or more gas 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 these lasers. Instead of a laser, another light source, an electron beam, or any other energy or radiation source suitable for solidifying the construction material can be used.

[0012] Furthermore, it can also be used in non-layer-by-layer generative devices that operate at a high process temperature to melt build-up material with a high melting point, such as laser cladding devices. In all of the above-mentioned cases, a device that uses an electron beam to generate the energy needed to melt the build-up material can be used instead of a laser device.

[0013] Metal-containing build-up materials are preferably used, for example, those containing iron and / or titanium, but also materials containing copper, magnesium, aluminum, tungsten, cobalt, chromium, and / or nickel. These elements can be present in almost pure form (making up more than 80 percent by weight of the build-up material) or as components of alloys.

[0014] A process chamber is defined as an area of ​​the manufacturing device in which the additive manufacturing process takes place and which is enclosed so that a different gas atmosphere can be maintained within it than that surrounding the manufacturing device. The process gas within the process chamber can, in particular, be an inert gas, such as nitrogen, helium, or argon. The process gas can also contain mixtures of various chemical elements, and the pressure in the process chamber can, if necessary, be below atmospheric pressure. It is also conceivable that the process gas contains other components in addition to inert gases.

[0015] The gas circulation system comprises a gas conveying device, e.g., a high-pressure fan or radial fan, and a gas line system by means of which the gas can be passed through the process chamber in a closed circuit, so that a gas flow can be provided in the process chamber during a manufacturing process.

[0016] When the gas circulation system is in operation, the gas conveying device ensures a continuous process gas flow, in which process gas, which has been passed through the process chamber, is fed to a filter system and from the filter system back to the process chamber, creating a closed gas circuit. The filter system contains at least one filter chamber through which the process gas flow is passed. The side of the filter chamber at which the process gas flow enters the filter chamber is hereinafter referred to as the raw gas side. The side of the filter chamber at which the process gas flow leaves the filter chamber again after passing through a filter element is hereinafter referred to as the clean gas side.

[0017] Each filter chamber contains at least one filter element, which means that a filter chamber can also contain two or more filter elements on which maintenance can be carried out after the filter chamber has been separated from the gas circuit.

[0018] The gas control device can contain a CPU whose operation is controlled by a computer program (software). The computer program can be stored on a storage medium from which it can be loaded into the gas control device. Alternatively, it is also possible to implement the gas control device in the form of a control program executed by a control unit used to control the additive manufacturing process in an additive manufacturing device. The prerequisite for this is that the corresponding control unit is connected via connecting cables or wirelessly to the hardware components by means of which filter chambers can be separated from the gas circuit. A wireless connection can be implemented via radio, WLAN, NFC, Bluetooth, or the like, provided the control unit has appropriate receivers and transmitters.

[0019] Ensuring that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit can be achieved, for example, via a control unit incorporated into the gas control device. It has been found that this assurance can improve the quality of the manufactured objects. A preliminary explanation for this is as follows:

[0020] To ensure high-quality manufactured objects, it is necessary for the manufacturing process to run as smoothly as possible and, moreover, for the process gas flow to be subject to as few fluctuations as possible during the manufacturing process. In other words, the volume flow in the gas circuit should be as constant as possible. If a number of filter chambers are arranged parallel to one another in a closed gas circuit, then each filter chamber contributes to an overall flow resistance due to the filter(s) arranged within it. This overall flow resistance results from the parallel connection of the flow resistances of the individual filter chambers. If individual filter chambers are separated from the gas circuit, the overall flow resistance changes suddenly. Especially with large volume flows, the ability of the gas delivery system to adapt the delivery rate to the changed overall flow resistance is limited.This leads to fluctuations in the volume flow through the process chamber and, as a result, to discontinuities or structural heterogeneities in the manufactured objects.

[0021] A high volume flow is generally accompanied by a high velocity of the process gas flowing through the process chamber. The procedure according to the invention guarantees that the process gas velocity remains essentially constant, i.e., fluctuates at most within a small interval. This ensures consistent removal of contaminants (spatter, smoke, etc.) arising during the build process if the procedure according to the invention is followed during a manufacturing process in the process chamber of the additive manufacturing device. However, ensuring that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit can, for example,This should be avoided when no construction process is taking place in the process chamber, but in order to avoid contamination of the process chamber from outside, a process gas flow is still maintained in the process chamber, albeit at a reduced process gas velocity.

[0022] By ensuring that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit, fluctuations in the volume flow when separating filter chambers can be limited, thus ensuring high quality of the manufactured objects. This is particularly true for high volume flows, which are advantageous in that the filter area can be increased, thereby extending the maintenance intervals of the filter elements (e.g., cleaning or replacing filter elements).

[0023] Ensuring that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers disconnected from the gas circuit can be implemented, for example, by checking, before disconnecting a filter chamber from the process gas flow, whether such a separation would result in the number of filter chambers remaining in the gas circuit no longer exceeding the number of filter chambers disconnected from the gas circuit, and only performing the separation if this is not the case. In other words, the gas control device prevents the maximum number of filter chambers disconnected from the process gas flow from being exceeded.

[0024] In particular, the value of this maximum number can be stored in a memory and adjusted when the total number Ntotai of filter chambers connectable to the process chamber changes. It should also be noted that this application often refers to cleaning or replacing filter elements with regard to the invention, but the present invention is not limited to this. Rather, it leads to advantages in all cases in which—for whatever reason—filter chambers are to be separated from the gas circuit or additionally integrated into it.

[0025] In a preferred embodiment, at least five filter chambers are provided, each with at least one filter element, and the device is designed to simultaneously isolate a plurality of filter chambers from the gas circuit for a maintenance operation (e.g., cleaning or replacing filter elements). This allows maintenance to be carried out more efficiently, since filter elements can be cleaned or replaced in parallel.

[0026] In a special embodiment, each of the filter chambers has at least one filter element for filtering particles in the gas circuit, which can be cleaned and / or replaced by a gas pressure surge.

[0027] Over time, a filter deposit consisting of a layer of compacted and / or adherent particles, commonly referred to as a "filter cake," forms on the filter elements. This filter cake impedes gas flow and leads to an ever-increasing pressure drop across the filter. Therefore, the most common maintenance procedure for a filter chamber is to reduce the pressure drop across the filter chamber. This is usually done by cleaning a filter element using a gas pressure pulse. Additionally or alternatively, the filter element containing the deposits can be removed from the filter chamber and replaced with another filter element without deposits. This usually requires opening the filter chamber so that components of the ambient atmosphere can enter the opened filter chamber and reach the filter element being replaced.The filter element itself preferably does not have a housing to prevent ambient air from entering the filter element when the filter element is replaced. In a specific embodiment, the plurality of filter chambers have a substantially identical volume and / or the filter elements have a substantially identical filter area and / or the same filter medium and / or the supply and discharge lines connected to the plurality of filter chambers have a substantially identical opening cross-sectional area.

[0028] In other words, the filter chambers with filter elements arranged therein without deposits preferably have the same flow resistance. This also preferably applies to the individual filter chamber combinations consisting of a filter chamber and individual supply and discharge lines to / from the filter chamber. In addition to the filter chamber, a filter chamber combination comprises all other elements which, together with the filter chamber, are arranged parallel to other filter chamber combinations in the gas circuit. The flow resistance of supply and discharge lines is determined in particular by the (minimal) opening cross-sectional area. An identical flow resistance can, for example, be realized in such a way that all filter chambers, in particular all filter elements, have the same structure, so that they contribute equally to the overall flow resistance when the filter chambers are arranged parallel to one another in the flow.In particular, the filter elements of all filter chambers can have the same filter medium, which means that the filter elements are made of the same material (e.g. fabric filter with 20pm polyester fibers or PE-S interfilter) and / or belong to the same filter class.

[0029] In a special embodiment, the gas control device is designed such that it ensures that during the ongoing manufacturing process, at least temporarily, preferably constantly, a numerical ratio of filter chambers not separated from the process gas circuit to filter chambers separated from the process gas circuit is 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, particularly preferably 4:1. The greater the ratio between filter chambers not separated from the process gas circuit to filter chambers separated from the process gas circuit, i.e. between filter chambers in the operating state of filtering the process gas to filter chambers not in the operating state of filtering the process gas, the smaller the fluctuation in the volume flow caused by the separation of a number of filter chambers.Therefore, it is preferable to specify a minimum ratio that must not be undercut, especially as the number of filter chambers increases—which, in principle, has no upper limit, meaning it can even go up to a few hundred or even 1,000. For example, if there are five filter chambers, a minimum ratio of 3:2 can be specified; if there are ten filter chambers, a minimum ratio of 60:40; or if there are 20 filter chambers, a minimum ratio of 55:45.

[0030] In a special design, all filter chambers in the gas circuit are always arranged in parallel to one another.

[0031] It is also possible for a plurality of filter chambers to be arranged one behind the other, and for this arrangement to be parallel to other filter chambers or further arrangements of filter chambers in series. With a series of filter chambers, upstream filter elements can prefilter the process gas, allowing downstream filter elements to perform fine filtration. For example, with a series of filter chambers, it is also possible to design only the upstream filter element(s) to be cleanable and / or replaceable.

[0032] In a special embodiment, the at least three filter chambers are sub-chambers of one or more main chambers of the filter system that are separated from one another in a gas-tight manner. For the overall flow resistance that is important within the scope of the present invention, it is irrelevant whether the plurality of filter chambers are spatially separated from one another or whether the plurality of filter chambers are sub-areas of a single chamber, the main chamber. In the latter case, it is only important that the sub-areas are separated from one another in a gas-tight manner so that the individual filter chambers can be independently sealed off from the gas circuit. Likewise, if the filter chambers are spatially separated, care should be taken to ensure that the flow resistances of the individual filter chambers do not differ too much from one another due to the supply and discharge lines of the individual filter chambers differing too greatly in flow resistance.Finally, it is also possible to provide a plurality of spatially separated main chambers with sub-areas therein, wherein the sub-areas each serve as a filter chamber.

[0033] In a special embodiment, for each of the at least three filter chambers, a switching unit is provided upstream and / or a switching unit downstream, by means of which this filter chamber can be sealed off from the gas circuit separately from the other filter chambers.

[0034] The gas control device is preferably designed such that it can control one or more switching units or valves upstream and / or one or more switching units or valves downstream of the plurality of filter chambers. This allows the gas control device to isolate one or more filter chambers from the gas circuit, for example during maintenance operations on the filter chambers, so that the process gas then only flows through the filter chambers still remaining in the gas circuit. A switching unit can, in particular, be a controllable valve, e.g., a pinch valve. The switching units can be controlled either via connecting lines or wirelessly. This can occur independently of a manufacturing process running in the additive manufacturing device.Although it is possible to seal off several filter chambers together from the gas circuit, there is more freedom if there is the option to seal off each filter chamber separately from the gas circuit.

[0035] In a special embodiment, a pressure sensor is provided for each of the at least three filter chambers upstream and downstream, so that a differential pressure between a raw gas side and a clean gas side of a filter element in the filter chamber can be determined.

[0036] By providing pressure sensors for each of the filter chambers, the filter element occupancy level can be derived separately from the differential pressure for each filter chamber, and a decision can be made individually for each filter chamber as to whether the filter element needs to be cleaned or replaced. Even though, theoretically, other components besides the filter element can influence the pressure difference determined by the pressure sensors, it is still the filter element that largely dominates the existing pressure difference.

[0037] In a special embodiment, in order to determine a differential pressure between a raw gas side and a clean gas side of a plurality of filter chambers, preferably all filter chambers, a pressure sensor is provided upstream of a fork in a feed line of the raw gas to the plurality of filter chambers and a pressure sensor is provided downstream of a junction of discharge lines of the clean gas from the plurality of filter chambers and the differential pressure is determined by comparing the pressure values ​​of the two pressure sensors.

[0038] The reduced number of pressure sensors results in a more cost-effective device.

[0039] In an even more specific embodiment, the gas control device is connected via signal connections to the pressure sensors upstream and downstream of a filter chamber and is configured to initiate cleaning of a filter element between these pressure sensors if a differential pressure received by the pressure sensors exceeds a predetermined maximum value.

[0040] With such a procedure, the device can automatically ensure that filter elements are maintained, such as cleaned or replaced. A signal connection can be either a signal line or a wireless connection (e.g., via radio, WLAN, NFC, Bluetooth, or the like), which allows communication between the gas control device and the pressure sensors, in particular the transmission of sensor values ​​to the gas control device. The differential pressure determined by the two upstream and downstream pressure sensors provides general information about the occupancy status of the filter elements arranged between the pressure sensors.If a plurality of filter chambers are arranged between the two pressure sensors, then if the predetermined maximum value is exceeded in all of these filter chambers, taking into account the number of filter chambers remaining in the gas circuit according to the invention, the filter elements can be cleaned or replaced.

[0041] In a special embodiment, a sensor for determining a 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 a filter element if a value of the volume flow received by the sensor falls below a predetermined minimum value.

[0042] An excessive drop in the volume flow of the process gas downstream of the filter system indicates that the filter system has excessive flow resistance due to clogging of the filter elements. An excessive drop in the volume flow can lead to insufficient removal of contaminants from the process chamber. If the volume flow sensor is connected to the gas control device via a signal connection, the device can automatically eliminate unwanted fluctuations in the volume flow (and thus the quality of the manufactured objects). The sensor for determining the volume flow can be used alternatively or as an additional backup alongside pressure sensors for determining a differential pressure upstream and downstream of filter chambers in order to initiate cleaning or replacement of filter elements.It would also be conceivable to place the volume flow sensor not downstream of the entire filter system, but downstream of a filter chamber or the convergence of the outlets of multiple filter chambers, thus allowing it to be used as an alternative or in addition to the pressure sensors upstream and downstream of the filter chambers. If, in addition to the values ​​from the sensor for determining the volume flow, the differential pressure values ​​applied to the individual filter chambers are also taken into account, the interaction of the information from the pressure sensors and the volume flow sensor can allow a fairly differentiated decision to be made as to which filter elements need to be cleaned or replaced and when.

[0043] In a special design, the gas circulation system has a fan.

[0044] The fan used as a gas conveying system can, in particular, be a high-pressure fan. In particular, the gas conveying system should preferably be designed so that it can react sufficiently quickly to changes in flow resistance (keep the volume flow sufficiently constant) when the flow resistance changes abruptly, for example, due to the removal of filter chambers from the gas circuit or the introduction of filter chambers into the gas circuit. In particular, the fan could be a radial fan.

[0045] An additive manufacturing device according to the invention with a process chamber for producing a three-dimensional object has a device according to the invention for providing a process gas atmosphere.

[0046] Such an additive manufacturing device allows the production of objects with improved quality. A method according to the invention for providing a process gas atmosphere during a manufacturing process of a three-dimensional object in a process chamber of an additive manufacturing device, in which the object is manufactured by applying a build-up material layer upon layer and solidifying the build-up material by supplying radiation energy to solidification points in each layer associated with the cross-section of the object in this layer, wherein, in the method for providing a process gas atmosphere, a process gas passed through the process chamber is moved by means of a gas circulation system in a closed gas circuit, wherein a filter system with a plurality of filter chambers is arranged in the closed gas circuit, is characterized in that at least three filter chambers are present,each of which has at least one filter element for filtering particles in the gas circuit, which can be cleaned by a gas pressure surge, and during the ongoing manufacturing process a number of filter chambers are separated from the gas circuit, ensuring that at least temporarily, preferably permanently, a number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit.

[0047] With regard to the details and advantages of such a method for providing a process gas atmosphere, what has been said above regarding a corresponding device for providing a process gas atmosphere applies.

[0048] In a special embodiment, in a filter chamber arranged in the gas circuit, the differential pressure applied to a filter element arranged therein is determined and cleaning is carried out on this filter element if the determined differential pressure exceeds a predetermined maximum value.

[0049] In particular, such an approach makes it possible to automatically ensure that filter elements are maintained during a manufacturing process, such as cleaning or replacement, without requiring user monitoring of the manufacturing process. The differential pressure measured by pressure sensors upstream and downstream of the filter chambers provides information about the occupancy status of the filter elements arranged between the pressure sensors. If exactly one filter chamber is located between two pressure sensors on which the differential pressure determination is based, the occupancy status can be determined in great detail.If a plurality of filter chambers are arranged between two pressure sensors on which the differential pressure determination is based, then if the predetermined maximum value is exceeded in all these filter chambers, taking into account the number of filter chambers remaining in the gas circuit according to the invention, the filter elements can be cleaned or replaced.

[0050] In a special design, the process gas is moved in a closed gas circuit with a volume flow that has a value of 50 m 3 / h, preferably 100 m 3 / h, further preferably 200 m 3 / h and / or a value of 2000 m 3 / h, preferably 500 m 3 / h, further preferably 400 m 3 / h.

[0051] From the perspective of optimal removal of contaminants from the process gas atmosphere in the process chamber caused by the irradiation of the build material, it would be desirable to select the highest possible value for the volume flow density. On the other hand, high volume flow density values ​​lead to increased turbulence of the build material. In practice, the target value for the volume flow density will therefore be set depending on the parameters selected for irradiating the build material and the build material used. The procedure according to the invention ensures that percentage fluctuations in the volume flow are kept within limits.

[0052] In a special embodiment, the value of a volume flow of the process gas in the closed gas circuit downstream of the filter system is determined and a filter element is cleaned when the determined value of the volume flow falls below a predetermined minimum value.

[0053] By directly monitoring the process gas flow rate, it is possible to immediately detect whether the flow rate exceeds the required range for high-quality manufacturing. This allows the occupancy status of the filter elements in the filter chambers to be determined independently of the pressure difference across the filter chambers.

[0054] In a specific embodiment, the filter system is connected to at least two process chambers of a number of additive manufacturing devices, with at least one centrifugal separator being particularly preferably assigned to each process chamber, with a manufacturing process for a three-dimensional object being carried out in each of the at least two process chambers at an overlapping time. The construction materials used in the process chambers can all be identical or different from one another. In particular, the filter system is fluidically connected to at least two process chambers. The term "fluidically connected" is intended to express that the connection is designed such that process gas can flow from the filter system to the additive manufacturing devices and vice versa.

[0055] In particular, the gas circuit can be designed such that the flow of filtered process gas coming from the filter system branches off to flow through the plurality of process chambers in parallel. Before the process gas to be filtered enters the filter system, the partial flows from the individual process chambers can then be recombined to be fed together to the filter system. Such an approach requires that the same process gas atmosphere is used in all process chambers. This is not a problem if the same construction materials are used in the process chambers, but even if different construction materials are used in the process chambers, it is still possible to use the same process gas, e.g., a protective gas such as argon.

[0056] A cyclone separator or centrifugal separator located near the process gas outlet of a process chamber or upstream of the process gas inlet of a filter system has the advantage of separating out coarse contaminants from the process gas stream before they contaminate, and in the worst case, clog, a piping system used for gas transport or the filter system. The process chambers can, in particular, belong to different additive manufacturing devices, for which a common (central) filter system is provided. Providing a common filter system reduces costs, as not every additive manufacturing device needs to be separately equipped with a complex filter system. In addition, the contaminants removed by the filters, as well as the contaminant-laden filters after replacement, are difficult to handle.Firstly, depending on the construction material used, spontaneous combustion or even explosions can occur upon contact with air. Secondly, the contaminant residues on the filters can also pose a health hazard to the personnel involved in their disposal. In any case, centralized handling of these hazardous substances makes it easier to dispose of them safely and with manageable risks, as complex equipment for handling the substances, such as a suitable protective gas atmosphere, only needs to be kept in one location.

[0057] Preferably, at least three process chambers are connected to the filter system and, in particular as long as a manufacturing process is taking place in one of the process chambers, it is ensured that a number of process chambers through which the process gas flows exceeds a number of process chambers through which the process gas does not flow.

[0058] In a case where the additive manufacturing processes in the different process chambers do not exactly overlap in time, in particular if they are of different durations, there is usually a desire to separate a process chamber in which, for example, the manufacturing process has already been completed from the process gas circuit in order to be able to remove the manufactured objects. This can also lead to abrupt changes in the flow resistance, which can be counteracted with the described procedure in order not to impair the manufacturing process in the process chambers through which the process gas is still flowing. A further method according to the invention serves to provide a process gas atmosphere during a manufacturing process of a three-dimensional object in a plurality of process chambers of a number of additive manufacturing devices, in each of which at least one object is manufactured.by applying a building material layer upon layer and solidifying the building material by supplying radiation energy to solidification points in each layer which are associated with the cross-section of the object in this layer, wherein a gas circulation system with a gas circuit which is closed during operation for a process gas passed through the process chambers is present, 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 at least one centrifugal separator is associated with each process chamber, wherein a manufacturing process for a three-dimensional object is carried out in each of the at least two process chambers in a temporally overlapping manner, wherein at least three process chambers are connected to the filter system and,in particular, as long as a manufacturing process is taking place in one of the process chambers, it is ensured 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.

[0059] In an additive manufacturing method according to the invention for producing a three-dimensional object in a process chamber of an additive manufacturing device, wherein the object is produced by means of the additive manufacturing device by applying a build-up material layer upon layer in the process chamber and solidifying the build-up material by supplying radiation energy to solidification points in each layer which are assigned to the cross-section of the object in this layer, a method according to the invention for providing a process gas atmosphere is used during the manufacturing method.

[0060] Such an additive manufacturing process allows the production of objects with improved quality. Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the accompanying drawings.

[0061] Fig. 1 shows a schematic, partially sectional view of an exemplary additive manufacturing device according to the invention with an exemplary device according to the invention for providing a process gas atmosphere.

[0062] Fig. 2 shows a schematic representation of an embodiment of a device for providing a process gas atmosphere.

[0063] Fig. 3 shows the representation of Fig. 2, wherein an exemplary arrangement of sensors in the gas circuit is also shown.

[0064] Fig. 4 illustrates an example procedure for cleaning a filter element.

[0065] Fig. 5 illustrates an exemplary process sequence for replacing or cleaning a number of filter elements.

[0066] With reference to Fig. 1, a basic structure of an additive manufacturing device to which the present invention relates is first described using the example of a laser sintering or laser melting device. The laser melting device 1 shown in Fig. 1 contains a process chamber 3 with a chamber wall 4 for building an object 2.

[0067] Arranged in the process chamber 3 is a container 5 with an upwardly open container wall 6. The upper opening of the container 5 defines a work plane 10, with the area of ​​the work plane 10 located within the opening, which can be used to build the object 2, being referred to as the build field. Arranged in the container 5 is a carrier 7 which is movable in a vertical direction V and to which a base plate 8 is attached, which closes off the container 5 at the bottom and thus forms its base. The base plate 8 can be a plate formed separately from the carrier 7 and fastened to the carrier 7, or it can be formed integrally with the carrier 7. Depending on the powder used and the process, a build platform 9 can be attached to the base plate 8 as a build base, on which the object 2 is built. However, the object 2 can also be built directly on the base plate 8, which then serves as the build base. In Fig.1, the object 2 to be formed in the container 5 on the construction platform 9 is shown below the working plane 10 in an intermediate state with several solidified layers, surrounded by unsolidified building material 11.

[0068] The laser melting device 1 further includes a storage container 12 for a powdered or pasty build material 13 that can be solidified by electromagnetic radiation, and a coater 14 movable in a horizontal direction H for applying the build material 13 within the build area. Preferably, the coater 14 extends transversely to its direction of movement over the entire area to be coated.

[0069] On its upper side, the wall 4 of the process chamber 3 contains a coupling window 15 for the laser beam 22 used to solidify the powder 13.

[0070] The laser melting device 1 further comprises an exposure device 20 with a laser 21 which generates a laser beam 22 which is deflected via a deflection device 23 and focused by a focusing device 24 via the coupling window 15 onto the working plane 10.

[0071] Furthermore, the laser melting device 1 has a control unit 29, via which the individual components of the laser melting device 1 are controlled in a coordinated manner to carry out the building process. The control unit can contain a CPU whose operation is controlled by a computer program (software). The computer program can be stored on a storage medium from which it can be loaded into the device, in particular into the control unit. In the present application, the term "control unit" includes any computer-based control unit capable of controlling or regulating the operation of an additive manufacturing device, in particular components thereof.The connection between the control unit and the controlled components does not necessarily have to be cable-based, but can also be implemented via radio, WLAN, NFC, Bluetooth or the like, provided that the control unit has corresponding receivers and transmitters.

[0072] During operation, to apply a layer of build material, the carrier 7 is first lowered by a height corresponding to the desired layer thickness. The coater 14 then moves over the build area and applies a layer of build material 13 to the build substrate or an existing layer of already selectively solidified build material. The application takes place at least over the entire cross-section of the object 2 to be produced, preferably over the entire build area, i.e., the area delimited by the container wall 6.

[0073] Subsequently, the cross-section of the object 2 to be manufactured is scanned by the laser beam 22, so that the powdered build-up material 13 is solidified at the locations corresponding to the cross-section of the object 2 to be manufactured. The energy introduced by the radiation partially or completely melts the powder grains at these locations, so that after cooling, they bond together as a solid. These steps are repeated until the object 2 is finished and can be removed from the process chamber 3.

[0074] As already mentioned at the beginning, depending on the type of build-up material used, particularly during sintering or melting of metal powder, spatter, smoke, vapors, and / or gases are generated during irradiation with the laser beam, which spread into the process chamber and impair the manufacturing process, also known as welding fumes. To prevent such impairments to the manufacturing process, a process gas flow is directed over the working plane 10. To generate a laminar gas flow 33 above the working plane 10, the laser melting device 1 therefore contains a gas supply channel 31, a gas inlet nozzle 32, a gas outlet nozzle 34, and a gas discharge channel 35. The gas supply and discharge can be controlled by a dedicated gas control device 80, which is shown separately from the control unit in Fig. 1, but control by the control unit 29 is also possible.The gas exiting the process chamber 3 is fed via the gas discharge channel 35 to a filter system 40, which filters out impurities (particularly metallic) from the process gas, and is then fed back to the process chamber 3 via the gas supply channel 31. A gas circulation system is formed by the gas supply channel 31, the gas inlet nozzle 32, the gas outlet nozzle 34, the gas discharge channel 35, and a gas conveying device 50, e.g., a circulation blower, in particular a high-pressure fan, which, during operation, enables a closed gas circuit for a process gas conveyed through the process chamber.

[0075] Fig. 2 shows a schematic representation of an example of a device for providing a process gas atmosphere in the process chamber. In addition to the gas circulation system, this device also includes the filter system 40 and the gas control device 80, which were already shown in Fig. 1 and are shown in more detail in Fig. 2. In the example of Fig. 2, the filter system 40 contains three filter chambers 41a, 41b, and 41c, which are shown in the figure as sub-chambers of a main chamber separated from one another in a gas-tight manner, but which can also be spatially separate chambers.

[0076] According to the invention, at least three filter chambers are provided. In other words, a larger number of filter chambers than shown in Fig. 2 can also be provided, and all explanations of the inventive approach in the present application are equally applicable to the presence of four, five, or more filter chambers that can be arranged parallel to one another in the process gas circuit.

[0077] Each filter chamber 41a, 41b, 41c contains a filter element 43a, 43b, or 43c. Fabric filters with 20 μm polyester fibers or PE sintered filters, for example, can be used as filter elements. Furthermore, each filter chamber contains a raw gas chamber 44a, 44b, or 44c, and a clean gas chamber 45a, 45b, or 45c on both sides of the filter element 43a, 43b, or 43c. The gas containing the contaminants (often referred to as raw gas) can be fed to each of the raw gas chambers 44a, 44b, or 44c via the gas discharge channel 35. The filtered gas (often referred to as clean gas) is fed from each of the clean gas chambers 45a, 45b, 45c via the gas supply channel 31 back to the process chamber 3, where it enters the gas inlet 32 ​​arranged in the chamber wall 4.

[0078] The gas inlets of the filter chambers are preferably designed so that the supplied gas flow is not directed directly onto a filter element. For example, the gas can be guided laterally into the filter chamber on a circular path. This utilizes a cyclone effect, and larger particles, such as components of the construction material (e.g., metal powder), never reach the filter element.

[0079] Furthermore, Fig. 2 shows the gas conveying device 50, e.g., a high-pressure fan, arranged in the gas circuit, with the flow direction in the gas circuit indicated by arrows. Not shown in the figure are a preferably present fine filter arranged upstream of the gas conveying device 50, as well as an optional particle separator, e.g., a centrifugal separator or cyclone separator, in the gas discharge channel 35.

[0080] Over time, the filtered-out particles accumulate on the mesh of a filter element 43a, 43b, or 43c. They are compressed by the pressure exerted by the process gas flow and, depending on the material and temperature, can agglomerate. Over time, a filter coating consisting of a layer of compressed and / or adhering particles forms, generally referred to as a "filter cake." The filter cake impedes gas flow and leads to an ever-increasing pressure drop across the filter, thus increasing the pressure difference between the raw gas and clean gas sides of the filter element, i.e., between the raw gas chamber 44a, 44b, or 44c and the clean gas chamber 45a, 45b, or 45c. The filter elements 43a, 43b, or 43c must therefore be cleaned from time to time to remove the filter cake, or replaced. An example cleaning procedure is explained using Fig. 4.This schematically shows a cleaning device 70 which has been brought into connection with the clean gas chamber 45a, 45b or 45c of a filter element 43a, 43b or 43c (in the figure, the clean gas chamber 45a and the filter element 43a are shown as examples).

[0081] To clean the filter element 43a, the cleaning device 70 generates a gas pressure pulse, which is introduced into the clean gas chamber 45a via the cleaning nozzle 71. For example, the cleaning device 70 can contain a pressure vessel with pressurized protective gas, from which individual gas pressure pulses are drawn as needed. A gas pressure pulse has, for example, a peak pressure of 5 or 10 bar and penetrates the filter element 43a to be cleaned, opposite 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 pulse acts on the filter cake from the outlet side of the filter element 43a. The filter cake is thereby detached from the filter element 43a across its entire surface, breaks into clumps, and is pushed away from the filter element 43a by the gas pressure pulse.The individual pieces of the filter cake fall downwards, attracted by gravity, and enter a collecting funnel 72, in the lower section of which is a closure 73, e.g., an iris diaphragm or a pneumatically / electrically controlled disc flap, with which the collecting funnel 72 can be sealed gas-tight at the bottom. Below this is a collecting container 74 (sometimes also referred to as a waste container). Optionally, a passivation nozzle 75 is provided, which can be used to fill the collecting container 74 with passivation material. However, the introduction of passivation material can also be omitted.

[0082] Furthermore, an optional protective gas nozzle (not shown in the figure) can be provided for introducing a protective gas, which can be identical to a protective gas used in the process chamber, into the collecting container 74. Further equipment details known to those skilled in the art are not shown in the schematic Fig. 4 for the sake of clarity, for example a vent used to inertize the filter chamber or a fill level sensor or a pressure sensor in the collecting container 74. As shown in Fig. 2, the gas discharge channel 35 splits into three sub-channels (without reference numerals), via which the gas to be filtered is supplied to the raw gas spaces 44a, 44b, 44c of the filter chambers 41a, 41b, 41c. Likewise, the outlets of the clean gas spaces 45a, 45b, 45c are merged in order to supply the filtered gas to the process chamber 3 via the gas supply channel 31. Here, the gas supply to the raw gas chambers 44a, 44b, 44c can be controlled via switching units 36a, 36b, 36c (e.g.The gas discharge from the clean gas chambers 45a, 45b, 45c can also be individually interrupted via switching units 37a, 37b, 37c (e.g., electromotively or electromagnetically actuated valves). This ensures that no ambient atmosphere enters the process gas atmosphere when a filter element is replaced, or that there are no negative effects on the pressure in the process chamber when filter elements are cleaned using a gas pressure pulse.

[0083] Fig. 2 shows a gas control device 80, which is connected to the switching units 36a, 36b, 36c and the switching units 37a, 37b, 37c by means of control lines shown in dashed lines (without reference numerals) in order to operate them. Although control lines are explicitly shown in the figure, it is understood that communication between the gas control device 80 and the switching units can also be wireless, for example, via radio, WLAN, NFC, Bluetooth, or the like, by the control unit and the switching units having 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.

[0084] In the event that one or more filter elements need to be cleaned or replaced, for example, filter element 43a, the gas control device 80 controls the corresponding switching units, 36a and 37a in the example, to disconnect the associated filter chamber 41a from the gas circuit through the process chamber 3. In doing so, 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 in the gas control device (e.g., implemented using software) is designed accordingly. In particular, it can check whether the number of filter chambers to be disconnected from the gas circuit through the process chamber 3 is greater than or equal to the number of filter chambers remaining in the gas circuit through the process chamber 3 and, if so, automatically disconnect a smaller number of filter chambers from the gas circuit.In particular, a step-by-step approach is also possible. This means that a check is first carried out to determine whether a number of filter chambers to be disconnected, reduced by 1, is still greater than or equal to the number of filter chambers remaining in the gas circuit through process chamber 3. If so, the number of filter chambers to be disconnected is reduced again by 1 to perform a new check. Only when the check shows that the number of filter chambers to be disconnected is smaller than the number of filter chambers remaining in the gas circuit will the current number of filter chambers to be disconnected be disconnected from the gas circuit.

[0085] To determine how many filter chambers are currently arranged in the gas circuit and / or how many are disconnected, the gas control device can check the switching state of the switching units 36a, 36b, 36c, 37a, 37b, or 37c. Irrespective of this, a value Nmax of the maximum permissible number of filter chambers that may be simultaneously disconnected from the gas circuit can be stored in a memory, e.g., in the gas control device. The gas control device then compares, for example, the number of filter chambers currently disconnected from the gas circuit with the value Nmax and sets, for example, a blocking flag if the value Nmax would be exceeded by disconnecting another filter chamber. The value Nmax of the maximum permissible number of filter chambers that may be simultaneously disconnected from the gas circuit can be fixed depending on the total number Ntotai of filter chambers that can be connected to the process chamber.Optionally, this value can be entered by a user of the additive manufacturing device before starting a manufacturing process, especially after changing the number of filter chambers available for filtering the process gas stream. In an alternative approach, when filter elements are to be cleaned or replaced, the maximum permissible number of filter chambers Nmax is always disconnected from the gas circuit. This also ensures that the number of filter chambers arranged in the gas circuit always exceeds the number of filter chambers not arranged in the gas circuit.

[0086] It goes without saying that a similar approach can be used if it is ensured that a numerical ratio (e.g., 2:1) of filter chambers not separated from the process gas circuit to filter chambers separated from the process gas circuit is not undercut. In such a case, the value of the variable Nmax can be adjusted accordingly.

[0087] Optionally, the gas control device 80 can emit a warning signal each time the number of filter chambers to be disconnected from the gas circuit through the process chamber 3 is greater than or equal to the number of filter chambers remaining in the gas circuit through the process chamber 3, or a numerical ratio of filter chambers not disconnected from the process gas circuit to filter chambers disconnected from the process gas circuit is exceeded. The warning signal can be an acoustic and / or an optical signal.

[0088] If there are three filter chambers, this means that at least two filter chambers are always present in the process gas circuit during the manufacturing process. If there are four or five filter chambers, this means that at least three filter chambers are always present in the process gas circuit during the manufacturing process. If there are six or seven filter chambers, this means that at least four filter chambers are always present in the process gas circuit during the manufacturing process.

[0089] Determining when a filter element should be replaced or cleaned can be done using sensors arranged upstream and downstream of a filter chamber in the gas circuit, as explained in Fig. 3. Fig. 3 is very similar to Fig. 2. The difference from Fig. 2 is that Fig. 3 also shows sensors 38a, 38b, 38c, 38g, 39a, 39b, 39c, and 39g, which have been omitted from Fig. 2 for clarity. Sensors 38a, 38b, 38c, 38g, 39a, 39b, 39c, and 39g are pressure sensors. By comparing the values ​​determined by the sensors 38a and 39a, 38b and 39b or 38c and 39c, the pressure difference applied to the associated filter chamber 41a, 41b or 41c can be determined.If the pressure difference across a filter chamber exceeds a specified maximum value, this can be used as an indicator that the filter element in the corresponding filter chamber should be replaced or cleaned.

[0090] Although the 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 across the entire set of filter chambers arranged parallel to one another in the gas circuit can be determined, and based on this pressure difference, a decision can be made as to whether or not a replacement or cleaning of any of the filter elements is necessary. It should be noted that, alternatively or additionally, the pressure difference for only a subset of the entire set of filter chambers arranged parallel to one another in the gas circuit can also be determined using two sensors upstream and downstream of this subset in the gas circuit.

[0091] In Fig. 3, for reasons of clarity, reference numeral 90 generally designates signal lines (dashed) between the sensors and the gas control device 80, via which pressure values ​​determined by the respective sensors can be transmitted to the gas control device 80, and signal lines between the gas control device 80 and the switching units. Based on the pressure values ​​transmitted by the sensors, the gas control device 80 can determine pressure differences present in the filter chambers and automatically decide when filter elements need to be replaced or cleaned. Even though signal lines are explicitly shown in the figure, it is understood that communication can also take place wirelessly, for example via radio, WLAN, NFC, Bluetooth, or the like, in that the gas control device and the switching units have corresponding receivers and transmitters.

[0092] Finally, Fig. 3 shows a sensor 51 for determining the volume flow in the gas circuit, which is also connected to the gas control device 80 via a signal connection. In Fig. 3, the sensor 51 is shown upstream of the gas conveying device 50, but it can alternatively be arranged downstream. If the sensor 51 indicates a drop in the volume flow below a predetermined minimum value, a decision can be made, regardless of the differential pressure values ​​determined by the pressure sensors, as to whether filter elements should be cleaned or replaced. However, if the differential pressure values ​​applied to the individual filter chambers are also taken into account for the decision, the interaction of the information from the pressure sensors and the volume flow sensor can be used to make a fairly differentiated decision as to which filter elements need to be cleaned or replaced and when.

[0093] With reference to Fig. 5, a possible process sequence for replacing or cleaning a number of filter elements using a correspondingly adapted gas control device 80 is described below. The starting point of the process sequence (step 50) is a point in time at which it was decided that a filter element in a plurality i of filter chambers needs to be replaced or cleaned. This decision can, for example, have been made automatically by the gas control device 80 based on the pressure differences prevailing in the individual filter chambers.

[0094] In step S1, following the decision, it is determined whether the number Ni of filter chambers in which a filter element must be replaced or cleaned is greater than or equal to half the total number Ntotai of filter chambers that can be connected to the additive manufacturing device during a manufacturing process. If so, a step S1' is executed in which it is checked whether a number NM of filter chambers would also be greater than or equal to half the total number of filter chambers. If this is not the case, method step S2 is executed next. If a number NM of filter chambers is also greater than or equal to half the total number of filter chambers, it is successively checked whether a number NI-2, NI-3, etc. of filter chambers is greater than or equal to half the total number of filter chambers until this is no longer the case for a number NH (j>1), and the method can then proceed to step S2.

[0095] In step S2, the gas control device 80 controls the switching units downstream and upstream of those i filter chambers in which the filter element is to be cleaned or replaced, in order to isolate these filter chambers from the gas flow. If method step ST has been performed, NM or NH filter chambers are isolated, not Ni.

[0096] In step S3, the filter elements in the separated filter chambers are cleaned or replaced in a known manner. Upon completion of the cleaning or replacement process, an end signal is transmitted to the gas control device 80. This occurs automatically during a cleaning process; this can also be the case during a replacement process, but can also be done manually. Upon receipt of the end signal, which indicates that a filter chamber is ready for operation again, the gas control device 80 then reopens the switching units downstream and upstream of this filter chamber in step S4, so that the process gas flows through the filter chamber again.

[0097] It should be noted that the filter chambers to be separated from the gas circuit may not necessarily be separated simultaneously, but may also be separated successively. This applies in particular in a case where the pressure differences between the individual filter chambers are not determined separately using sensors upstream and downstream of each filter chamber, but rather the resulting pressure difference between several filter chambers arranged parallel to one another in the gas flow is determined, for example, using sensors 38g and 39g in Fig. 3. Furthermore, the pressure difference described with reference to Fig.The procedure described in paragraph 5 can be carried out in the same way if, instead of checking whether the number Ni of filter chambers in which a filter element has to be replaced or cleaned is greater than or equal to half the total number Ntotai of filter chambers, it is checked whether the numerical ratio of the difference between the total number Ntotai of filter chambers and the number Ni to the number Ni, in other words (Ntotai-Ni) / Ni, is less than a predetermined minimum value or not.

[0098] Finally, it should be noted once again that the devices described in detail above are merely exemplary embodiments that can be modified in a variety of ways by those skilled in the art without departing from the scope of the invention. For example, solidification could be carried out using other energy beams instead of laser light. Furthermore, the use of the indefinite articles "a" or "an" does not exclude the possibility that the respective features may be present in multiple instances. Likewise, the term "unit" does not exclude the possibility that it consists of several interacting subcomponents, which may also be spatially distributed. The expression "a number" is to be understood as "at least one."

Claims

Patent claims 1. Device for providing a process gas atmosphere during a manufacturing process of a three-dimensional object (2) in a process chamber (3) of an additive manufacturing device, in which the object is manufactured by applying a build-up material (13) layer upon layer and the build-up material is solidified by supplying radiant energy to solidification points in each layer, which are associated with the cross-section of the object in that layer, wherein the device for providing a process gas atmosphere comprises a gas recirculation system with a closed gas circuit for a process gas passed through the process chamber (3), wherein a filter system (40) with a plurality of filter chambers (41a, 41b, 41c) is arranged in the closed gas circuit, characterized in that at least three filter chambers are provided, each of which contains at least one filter element (43a, 43b,43c) for filtering particles in the gas circuit, and a gas control device (80) for controlling the gas circuit is provided, which is configured to be able to isolate a number of filter chambers (41a, 41b, 41c) from the gas circuit during the manufacturing process and to ensure that at least temporarily, preferably continuously, the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers isolated from the gas circuit.

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

3. Device according to claim 1 or 2, wherein the plurality of filter chambers (41a, 41b, 41c) have a substantially equal volume and / or the filter elements (43a, 43b, 43c) have a substantially identical filter area and / or have a similar filter medium and / or the inlets and outlets connected to the majority of filter chambers (41a, 41b, 41c) have a substantially identical opening cross-sectional area.

4. Device according to one of the preceding claims, wherein the gas control device (80) is configured to ensure that, during the ongoing manufacturing process, at least temporarily, preferably continuously, the ratio of filter chambers not separated from the process gas circuit to filter chambers separated from the process gas circuit is 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. Device according to one of the preceding claims, in which all filter chambers (41a, 41b, 41c) arranged in the gas circuit are always arranged in parallel to each other.

6. Device according to one of the preceding claims, wherein the at least three filter chambers (41a, 41b, 41c) are gas-tightly separated sub-chambers of one or more main chambers of the filter system (40).

7. Device according to one of the preceding claims, in which a switching unit (36a, 36b, 36c) is provided upstream for each of the at least three filter chambers (41a, 41b, 41c) and / or a switching unit (37a, 37b, 37c) is provided downstream, by means of which each of these filter chambers can be isolated separately from the other filter chambers from the gas circuit.

8. Device according to one of the preceding claims, in which a pressure sensor (38a, 38b, 38c, 39a, 39b, 39c) is provided upstream and downstream for each of the at least three filter chambers (41a, 41b, 41c) so that a differential pressure between a raw gas side and a clean gas side of a filter element (43a, 43b, 43c) in the filter chamber (41a, 41b, 41c) can be determined.

9. Device according to one of claims 1 to 7, in which, for determining a differential pressure between a raw gas side and a clean gas side of a plurality of filter chambers, preferably all filter chambers, a pressure sensor (38g) is provided upstream of a fork in a supply line of the raw gas to the plurality of filter chambers and a pressure sensor (39g) is provided downstream of a merging of outlets of the clean gas from the plurality of filter chambers and the differential pressure is determined by comparing the pressure values ​​of the two pressure sensors.

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

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

12. Device according to one of the preceding claims, wherein the gas circulation system comprises a fan (50).

13. Additive manufacturing device comprising: a process chamber (3) for manufacturing a three-dimensional object, wherein the additive manufacturing device is a device according to one of the claims 1 to 12.

14. Method for providing a process gas atmosphere during a manufacturing process of a three-dimensional object (2) in a process chamber (3) of an additive manufacturing device, in which the object is manufactured by applying a build-up material (13) layer upon layer and the build-up material is solidified by supplying radiant energy to solidification points in each layer, which are associated with the cross-section of the object in that layer, wherein in the method for providing a process gas atmosphere a process gas passed through the process chamber (3) is moved in a closed gas circuit by means of a gas recirculation system, wherein a filter system (40) with a plurality of filter chambers (41a, 41b, 41c) is arranged in the closed gas circuit, characterized in that at least three filter chambers are provided, each of which contains at least one filter element (43a, 43b,43c) for filtering particles in the gas circuit which can be cleaned by a gas pressure pulse, and during the manufacturing process a number of filter chambers (41a, 41b, 41c) are separated from the gas circuit, ensuring that at least temporarily, preferably continuously, the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit.

15. Method according to claim 14, in which the differential pressure applied to a filter element (43a, 43b, 43c) arranged in a filter chamber (41a, 41b, 41c) in the gas circuit is determined and cleaning is carried out on this filter element when the determined differential pressure exceeds a predetermined maximum value.

16. Method according to claim 14 or 15, wherein the process gas is moved in a closed gas circuit with a volume flow rate of 50 m³ / h.3 / h, preferably 100 m 3 / h, preferably 200 m 3 / h exceeds and / or a value of 2000 m 3 / h, preferably 500 m 3 / h, preferably 400 m 3 / h falls below.

17. Method according to one of claims 14 to 16, wherein the value of a volume flow rate of the process gas in the closed gas circuit downstream of the filter system (40) is determined and a cleaning of a filter element (43a, 43b, 43c) is then carried out when the determined value of the volume flow rate falls below a predetermined minimum value.

18. Method according to one of the preceding claims, wherein the filter system (40) is connected to at least two process chambers (3a, 3b) of a number of additive manufacturing devices, wherein at least one centrifugal separator is particularly preferably assigned to each process chamber (3a, 3b), wherein a manufacturing process of a three-dimensional object is carried out in each of the at least two process chambers (3a, 3b) in a temporally overlapping manner.

19. Method according to claim 18, wherein at least three process chambers are connected to the filter system (40) and, in particular while a manufacturing process is taking place in one of the process chambers, it is ensured that a number of the process chambers through which the process gas flows exceeds a number of the process chambers through which the process gas does not flow.

20. Additive manufacturing process for producing a three-dimensional object in a process chamber of an additive manufacturing device, wherein the object (2) is produced by means of the additive manufacturing device by applying a build-up material (13) layer upon layer in the process chamber (3) and solidifying the build-up material by supplying radiant energy to solidification points in each layer, which are associated with the cross-section of the object in that layer, wherein during the manufacturing process a method according to one of the Claims 14 to 19 are applied.

Images