EP4168154A1

EP4168154A1 - Filter device for an additive manufacturing device

Info

Publication number: EP4168154A1
Application number: EP21731718.9A
Authority: EP
Inventors: Ulrich Kleinhans; Philip STRÖBEL
Original assignee: EOS GmbH
Current assignee: EOS GmbH
Priority date: 2020-06-17
Filing date: 2021-06-02
Publication date: 2023-04-26
Also published as: CN115697523A; US20230264263A1; DE102020116030A1; WO2021254783A1

Abstract

The invention relates to a filter device (100) for an additive manufacturing device (1) for purifying a process gas (50) of the additive manufacturing device (1), wherein the filter device (100) has at least one permanent filter (41) for purifying a volume of process gas (50) during operation, and wherein the permanent filter (41) is configured to be temperature-resistant in such a way that a temperature resistance of the permanent filter (41) during operation is higher than 110°C. The invention furthermore relates to an additive manufacturing device and to a method for additive manufacturing.

Description

Filter device for an additive manufacturing device

The present invention relates to a filter device for an additive manufacturing device, an additive manufacturing device with such a filter device, and a method for the additive manufacturing of a component.

In the production of prototypes and now also in series production, additive manufacturing processes are becoming more and more relevant. In general, “additive manufacturing processes” are those manufacturing processes in which a manufactured product or component is built up by adding material, usually on the basis of digital 3D design data. The build-up usually takes place in that a build-up material is applied in layers and selectively solidified. The term “3D printing” is often used as a synonym for additive manufacturing, the production of models, samples and prototypes using additive manufacturing processes is often referred to as “rapid prototyping” and the production of tools as “rapid tooling”.

The selective solidification of the building material often takes place in that thin layers of the mostly powdery building material are repeatedly applied one on top of the other and by spatially limited irradiation, e.g. B. by means of light and / or thermal radiation, is solidified at the points that should belong to the product to be produced after manufacture. Examples of processes that use radiation are “selective laser sintering” or “selective laser melting”. The powder grains of the build-up material are partially or completely melted in the course of solidification with the help of the energy introduced locally by the radiation at this point. After cooling, these powder grains are then connected to one another in the form of a solid.

With such a production it is often necessary that a process gas for cooling or discharge purposes (in particular with a fan) is led through the process chamber. The escaping process gas usually carries with it particles of the build-up material and / or particles formed during the process, in particular metal condensates when using metallic build-up materials, some of which are highly reactive and can react with small amounts of atmospheric oxygen with high heat release even at room temperature . In order to prevent contamination of the process gas with the particles, for example to counteract creeping contamination of the process chamber and / or the fan, it is necessary to filter the process gas after it exits the process chamber. Due to the high reactivity of the particles, however, uncontrolled filter fires or dust explosions can occur in the area of filters where the particles carried along in the process gas collect. This risk is increased if, for example, a corresponding filter chamber is opened to change the filter or filters, which increases the likelihood of a reaction due to the associated increased supply of oxidizing agent, for example atmospheric oxygen.

It is an object of the present invention to provide an improved or alternative filter device or a manufacturing device provided with a filter, which enables a safe filter removal when changing the filter in an additive manufacturing device.

This object is achieved by a filter device for an additive manufacturing device according to claim 1, a corresponding additive manufacturing device according to claim 10, and by a method for additive manufacturing according to claim 11.

The invention is concerned with the field of additive manufacturing, in which this manufacturing takes place in a (closed) process chamber through which a process gas is passed, which is then filtered. Process gas is understood here as the gas discharged, in particular extracted, from a process chamber, which, depending on the manufacturing process, can also be or include an inert gas. The process gas can contain both non-solidified parts of a building material and process by-products such as condensates, for example metal condensates. Such components carried along in the process gas are summarized under the term “particles”.

A filter device according to the invention for an additive manufacturing device serves to purify a process gas from the additive manufacturing device. To purify a volume of process gas during operation, the filter device has at least one (dimensionally stable) permanent filter which is temperature-resistant, preferably burn-off-resistant, so that the permanent filter has a temperature resistance of more than 110 ° C. during operation. In the context of the invention, permanent filters (or “permanent filters”) are understood to mean filters which, in contrast to conventional filter models, can often remain in operation of the additive manufacturing device (over many cycles) and / or permanently. For this purpose, a permanent filter is cleaned after a certain period of time, i.e. the filtrate is removed or rejected and the filtrate is removed from the filter pores or the filter material and / or a filter cake lying on the filter. A permanent filter must contain a filter material that has such a high mechanical strength that it is not destroyed or damaged when it is cleaned as intended. An example of a permanent filter is (or comprises) a metal filter with a metal grid or metal sieve as the filter material or a filter with a filter medium made of glass wool or ceramic. In particular, a filter with a polyester fabric is not to be regarded as a permanent filter, at least if it does not have sufficient mechanical and thermal resistance. The advantage of a permanent filter is that the risk of fire due to the heating of dusty filtrate is significantly reduced, on the one hand due to the generally comparatively good heat conduction of the filter material and on the other hand due to the fact that a permanent filter does not have to be replaced and is cleaned under clearly defined, inert conditions can be carried out. Cleaning can be done e.g. B. be done in that a pressure surge occurs against the process gas direction, z. B. with an inert gas such as nitrogen, and thereby the pore-clogging filtrate and / or a filter cake lying on the filter is removed from the filter and can fall into a container. The good heat conduction of the permanent filter has a positive effect in particular when reactions can occur due to the penetration of oxidizing agents, for example oxygen, due to existing leaks in a system and / or when changing the filter and / or when opening the process chamber .

An additive manufacturing device according to the invention for manufacturing a component in an additive manufacturing process comprises a process room, a feed device for introducing a build-up material into the process room in layers, an irradiation unit for the selective solidification of build-up material in the process room and a filter device according to the invention for cleaning a (emerging from the process room) ) Process gas of the additive manufacturing device.

A method according to the invention for additive manufacturing of a component in an additive manufacturing process by means of an additive manufacturing device comprises the following steps: - Introducing at least one layer of a construction material into a process space of the manufacturing device,

- Selective solidification of the building material in the process space by means of an irradiation unit and

- Purification of a volume of a process gas (exiting the process space and in particular moving in a closed circuit) of the additive manufacturing device by means of a filter device according to the invention.

According to the invention, use of a permanent filter for purifying process gas in a filter device for an additive manufacturing device is also preferred, preferably for use in a filter device according to the invention.

According to the invention, a permanent filter is also designed for purifying process gas in a filter device for an additive manufacturing device, preferably for purifying process gas in a filter device according to the invention.

Further, particularly advantageous refinements and developments of the invention can be found in the dependent claims and the following description, with the independent claims of one claim category also being able to be developed analogously to the dependent claims and exemplary embodiments of another claim category and, in particular, individual features of various types management examples or variants to new embodiments or variants can be combined.

According to a preferred filter device, the permanent filter is designed to be temperature-resistant so that the temperature resistance of the permanent filter is higher than 150 ° C, preferably higher than 250 ° C, preferably higher than 350 ° C, particularly preferably higher than 500 ° C.

Accordingly, the purification of process gas takes place according to a preferred method for additive manufacturing at a process gas temperature of more than 40 ° C, preferably at a process gas temperature of more than 110 ° C, preferably at a process gas temperature of more than 150 ° C, preferably at a Process gas temperature of more than 200 ° C, particularly preferably at a process gas temperature of more than 250 ° C, particularly preferably at a process gas temperature of more than 300 ° C.

The process gas temperature is preferably in the range from 40 ° C to 60 ° C. However, a higher process gas temperature is also conceivable. Depending on the type of construction material and the filter, a preferred temperature range is between 0 ° C and 1000 ° C, in particular between 40 ° C and 250 ° C or even between 60 ° C and 100 ° C. The temperature resistance of the permanent filter must be higher than the process gas temperature.

According to a preferred filter device, the permanent filter is designed to be dimensionally stable in such a way that a working time of the permanent filter is essentially constant when the filter device is in operation. Working time refers to the time between necessary cleanings of the filter, i.e. the time in which the filter can perform its task as intended. In the case of a commercially available filter, this would correspond to the service life, i.e. the time until the filter has to be replaced after a few, for example 200, cleanings. Since a permanent filter basically does not have to be replaced, we speak of working hours here.

According to a preferred filter device, the permanent filter comprises a metal filter, the metal filter preferably being formed from at least one steel, in particular corrosion-resistant steel, and / or from a nickel-based alloy and / or from copper and / or from mixtures or alloys thereof. A preferred corrosion-resistant steel is stainless steel. The advantage of a metal filter is the good temperature and oxidation resistance and the comparatively high thermal conductivity, which prevents spontaneous ignition of the condensate and / or withstands it better or slows it down. Corrosion resistance is advantageous because in this case the filter can be heated and the filtrate can be oxidized in a controlled manner. Further advantages of a metal filter are its high strength / inherent rigidity, which supports the basic function of the permanent filter and leads to a long service life even with many cleanings (many pressure surges), a smooth surface structure that allows easy cleaning because the filter cake is only loosely attached , high abrasion resistance and no particle detachment. In addition, a metal filter allows a good flow, which leads to a low pressure loss across the filter and the filter can therefore be more heavily occupied compared to other filter fabrics that have high pressure losses (low flow rates). A metal filter also has chemical and thermal resistance, which significantly reduces the risk of fire. In addition, would also be Operation at higher gas temperatures (greater than 500 ° C or even greater than 800 ° C) is conceivable. The metal filter preferably has a defined, in particular regular arrangement of the filter pores and is preferably made of a braided fabric or a perforated plate or a grid. A narrow pore size distribution with more than 50 pores per square cm, in particular more than 100 pores per square cm, is also preferred.

According to a preferred filter device, the permanent filter comprises a ceramic filter and / or a glass wool filter as an alternative to or in addition to a metal filter. A mixture of different filter types (i.e. metal filters, ceramic filters and glass wool filters) is preferred depending on the application. This could z. B. the good thermal conductivity of a metal filter combined with the advantages of a ceramic or glass wool filter who the. For example, different filter stages can be formed in one filter.

According to a preferred filter device, a mesh size (or pore size) of a filter material of the permanent filter is not more than 30 μm, preferably not more than 20 μm, preferably not more than 8 μm. The mesh size (or pore size) is preferably at least 0.5 μm, preferably at least 1 μm, preferably at least 2 μm, particularly preferably 3 μm. It should be noted here that too large a mesh size results in inadequate filtration. If it is too small, the pressure losses are too great and the gas flow through the filter is no longer sufficient.

According to a preferred filter device, the permanent filter has filter structures with a preferred diameter between 1 μm and 1000 μm.

According to a preferred filter device, a (wire) diameter of fibers which form a filter material of the permanent filter is less than 100 μm, preferably less than 50 μm, preferably less than 20 μm, in particular less than 10 μm, particularly preferably less than 5 μm. In this case, however, the diameter is preferably greater than 1 μm.

If the metal filter comprises a grid of metal wires, metal wire diameters of at least 1 μm are preferred, but preferably thinner than 100 μm, depending on the application. Metal wires with the aforementioned preferred dimensions for fibers are preferably present. The permanent filter can additionally comprise a support structure which is designed to support the permanent filter (in particular its filter surface), to keep it in shape and / or to increase the mechanical strength of the filter material. Such a support structure is particularly advantageous when cleaning a permanent filter by means of a pressure surge. Of course, such a support structure must not significantly impair the function of a filter. Therefore, the support structure is preferably constructed like a grid or a sieve, e.g. B. in the form of a wire mesh or a perforated sheet-like element, e.g. B. a perforated plate. If a support structure comprises wires, these are preferably thicker than the fibers / wires of the filter material and preferably have a thickness of more than 100 μm, preferably more than 200 μm, but preferably less than 1000 μm, in particular less than 700 μm.

According to a preferred embodiment, the support structure runs parallel to the filter material of the permanent filter and preferably runs at least in a partial area on its dirty gas side and / or on its clean gas side. Because contamination of the support structure must also be expected on the dirty gas side, but also for better gas passage it preferably has a lattice structure with a mesh size greater than 1 mm.

The support structure can, however, also be integrated in the filter material, preferably in the form of reinforced or stronger elements of the filter material. In this regard, a filter material is preferred which comprises a support structure composed of wires arranged in parallel or in a grid-like manner, e.g. B. a cylindrical filter which comprises rings made of wires of the support structure in its outer surface or a pleated filter with star-shaped wires of the support structure. Also preferred is a grid of parallel (warp) wires in one direction and (weft) wires interwoven with them running orthogonally or at an angle thereto. According to a preferred embodiment, at least some (warp) wires are wires of the support structure (preferably with a thickness between 0.1 mm and 0.5 mm), with thinner (warp) wires of the filter material running between these (warp) wires (preferably with a thickness between 1 pm and 100 pm). The (weft) wires are then preferably wires of the filter material, with some (weft) wires particularly preferably also being able to be wires of the support structure. In this way, the support structure forms a coarse grid into which the filter material is woven as a finer grid.

A permanent filter is preferably designed in such a way that it provides sufficient filtration with a filter surface load between 0.2 m / min and 1.3 m / min (volume flow / filter surface). As far as the filter surface loading by the process gas is concerned, a lower value is advantageous over a higher value. Values that are too low mean, however, that the filter surface remains unused and thus unnecessary costs. Therefore, during operation, a filter surface loading of 0.2 to 1.3 m / min is preferred, preferably less than 0.8 m / min, more preferably less than 0.6 m / min.

The thermal conductivity of the permanent filter, at least its filter material, in particular that of the wires or fibers of a braid, is preferably greater than 0.5 W / (m - K), in particular greater than 10 W / (m - K), particularly preferably greater than 20 W / (m · K). This has the advantage that the danger of a fire from the filtrate is reduced by the rapid dissipation of local heat. Since z. B. with a polyester filter, the heat dissipation is not very good, ignition takes place even at lower Temperatu ren than with such a permanent filter.

According to a preferred filter device with a fiber fabric, the braiding is regular and / or chaotic. The advantage of such a construction is a robust structure, little damage during cleaning and therefore a particularly good longevity.

According to a preferred filter device, a dirty gas side of the permanent filter that comes into contact with the process gas to be purified has, at least in some areas, a, preferably meandering, pleated surface. In this case, a number of folds are preferably arranged in the surface in order to form a pleated surface on the dirty gas side. The folds for pleating are particularly preferably folds in a continuous fabric. Alternatively, the folds are preferably welded and / or glued together. The outer fabric is therefore pleated with respect to this preferred embodiment and not bent into curves (even if this can be preferred in other applications). Pleating increases the filter area significantly with the same volume, z. B. by a factor of 2 to 3. There is also a non-linear relationship between filter area and service life. A doubling of the filter surface (e.g. by pleating) can lead to 4 to 8 times longer service times. The folds are preferably so narrow that as much filter surface as possible is accommodated per cartridge and so wide that the filtered condensate can still be cleaned easily (ie comes out of the folds) when cleaning by pressure surge. Before given, a filter comprises 100 to 300 folds with a filter diameter of at least 20 cm. Even if a higher value for the number of folds is better, it must be noted that that a fold that is too tight has a negative effect on the cleanability of the filter. The depth of the folds is preferably at least 20 mm, more preferably at least 30 mm.

According to a further preferred filter device has a coming into contact with the process gas to be cleaned dirty gas side of the permanent filter at least be richly a rounded meander shape, for. B. a wave shape or a mäan such rectangular shape. The width of the respective structures (corresponds to a wavelength of a wave structure) is preferably greater than 1 cm, preferably greater than 2 cm and / or preferably less than 10 cm, preferably less than 4 cm. The depth of the structures is preferably at least 20 mm, more preferably at least 30 mm. A filter preferably comprises 100 to 300 of these structures with a filter diameter of at least 20 cm.

A filter surface of a single permanent filter is preferably at least 0.5 square meters, preferably at least 1 square meters, particularly preferably at least 3 square meters (square meters = square meters). For large systems with high volume flows, more area is useful, but this can also be achieved by connecting several filters in parallel and / or connecting several filter chambers in parallel. Since the susceptibility of the filter to mechanical loads increases with a larger area, the filter surface is preferably a maximum of 20 square meters, in particular a maximum of 3 square meters per cartridge, e.g. B. 2 square meters per cartridge.

According to a preferred filter device, the permanent filter is a cartridge filter and / or a plate filter with a preferably meandering cross section.

According to a preferred filter device, the permanent filter is arranged in the filter device in such a way that a dirty gas side that comes into contact with the process gas to be purified is an outer surface of the permanent filter.

Alternatively or in addition, the permanent filter is preferably arranged in the filter device in such a way that a dirty gas side coming into contact with the process gas to be purified is an inner surface of the permanent filter (located inside the filter). This variant of the internal dirty gas side has the advantage that the cleaned off condensate remains on the inside of the filter, which results in a reduced risk of fire when changing and therefore a lower risk for the operator in the event of incorrect service. In addition, in the case of inerting when removing the filter plates, the inert gas can be used more effectively (that is to say in a cost-saving manner due to lower volumes required) by being introduced on the inside of the filter plates. A solid inert agent would also be conceivable, for example sand and / or expanded glass granulate. The advantage of a variant with an outer and an inner filter surface is the gain in filter surface with the same outer circumference.

According to a preferred filter device, the permanent filter is designed in such a way that particles removed from the permanent filter can be used (directly) as building material in a (new) additive manufacturing process. The metal condensate, which is collected in a collecting container after the filter has been cleaned, can optionally be recycled without purification, in particular because metal filters have untreated surfaces.

According to a preferred filter device, the permanent filter is designed in such a way that an oxidation reaction of particles present in the permanent filter can be initiated (triggered), the permanent filter preferably being coupled to a source of energy input, and preferably a metal mesh, or part of a metal mesh of the permanent filter Represent heating element. In particular, the filter comprises insulated wires (for example in a braid) which represent the heater. A metal mesh of the filter is preferably used as an active resistance heater. The advantage of such heating is that chemical processes such as B. an oxidation can be stimulated in a controlled manner, so that a targeted or controlled reaction of the filter cake directly on the filter it can be enough.

According to a preferred embodiment, the permanent filter, in particular a metal filter of the permanent filter, comprises a surface coating. The surface coating, for example a PTFE membrane coating, preferably has the function that the adhesive forces with which the particles, eg. B. metal condensate or Me tallpulver, adhere to the surface of the permanent filter, are reduced and thus increases the cleanability or reduces from the outset the deposition of particles and creates increased surface filtration. An exemplary surface coating is or comprises a vapor-deposited PTFE layer, preferably with a thickness in the nanometer range (preferably thicker than 1 nm, preferably thinner than 1000 nm). With such a thin surface coating there is no additional risk of fire. The surface coating is preferably an initial filter cake, e.g. Legs Layer of extremely fine, sintered metal, this layer in turn prevents the accumulation of dust. This turns the permanent filter into a surface filter.

In a preferred method for additive manufacturing, process gas is purified and / or the permanent filter is cleaned so that particles removed from the permanent filter can be used as construction material in a (renewed) additive manufacturing process.

The permanent filter of the filter device is preferably designed and arranged in the filter device in such a way that the permanent filter can be cleaned in a cleaning operation of the filter device running parallel to a construction process of the manufacturing device. A related "online cleaning", i.e. cleaning without a construction job interruption, is preferably carried out at a lower pressure than cleaning during an interruption in the construction job or between construction jobs, which should take place at approx. 5 bar. A preferred pressure range for online cleaning is between 2 and 5 bar.

At least two filter chambers connected in parallel are preferably used, one of which is separated from the gas flow during cleaning. For example, the area around this could be enriched with oxygen in a controlled manner (and this filter chamber heated) and the filter cake oxidized in a controlled manner without endangering or influencing the construction process.

In a preferred method for additive manufacturing, the permanent filter is cleaned during the (ongoing) additive manufacturing process, in particular without interrupting the manufacturing process.

In a preferred method for additive manufacturing, the permanent filter is cleaned as a function of a differential pressure value of the process gas (via the permanent filter). For this purpose, a preferred differential pressure value is at least 10 mbar, preferably at least 20 mbar, preferably at least 30 mbar, particularly preferably at least 40 mbar. Alternatively or additionally, a cleaning pressure surge for cleaning the permanent filter is less than 5 bar, preferably less than 4 bar, preferably less than 3 bar, particularly preferably 2.5 bar. However, this pressure depends on the area and shape of the permanent filter. It can also be preferred that a cleaning pressure surge more than 2 or preferably more than 3 bar, in particular more than has 4 bar. The filter device preferably comprises buffer volumes which absorb the pressure surge.

The invention is explained in more detail below with reference to the accompanying figures on the basis of exemplary embodiments. The same components are provided with identical reference numbers in the various fi gures. The figures are usually not to scale. Show it:

Figure 1 is a schematic, partially shown in section view of a device for the generative production of a three-dimensional object,

FIG. 2 shows a schematic, partially sectioned view of a filter device for filtering in a process gas,

FIG. 3 shows a schematic view, partially shown in section, of a filter device for filtering in a process gas,

Figure 4 is a schematic, sectional view of Figure 3,

FIG. 5 shows a schematic, sectional side view of a filter device for filtering in a process gas,

FIG. 6 shows a schematic, perspective illustration of a further preferred permanent filter in the form of a plate filter.

In the following, a device for the generative production of a three-dimensional object is described with reference to FIG. 1. The device shown in FIG. 1 is a laser sintering or laser melting device 1. To build up an object 2, it contains a process chamber 3 with a chamber wall 4.

A container 5, which is open at the top and has a container wall 6, is arranged in the process chamber 3. A working plane 7 is defined by the upper opening of the container 5, the area of the working plane 7 lying within the opening, which can be used to build the object 2, is referred to as construction field 8. In addition, the process chamber 3 comprises a process gas supply 31 assigned to the process chamber and an outlet 53 for process gas. In the container 5 there is arranged a carrier 10 which is movable in a vertical direction V and to which a base plate 11 is attached which closes the container 5 at the bottom and thus forms its bottom. The base plate 11 can be a plate formed separately from the carrier 10 and attached to the carrier 10, or it can be formed integrally with the carrier 10. Depending on the powder and process used, a construction platform 12 can also be attached to the base plate 11 as a construction base, on which the object 2 is built. The object 2 can, however, also be built on the base plate 11 itself, which then serves as a construction base. In FIG. 1, the object 2 to be formed in the container 5 on the construction platform 12 is shown below the working plane 7 in an intermediate state with several solidified layers, surrounded by building material 13 that has remained unsolidified.

The laser sintering device 1 also contains a storage container 14 for a powdery build-up material 15 which can be solidified by electromagnetic radiation and a coater 16 movable in a horizontal direction H for applying the build-up material 15 within the construction field 8. The coater 16 preferably extends across its direction of movement the whole area to be coated.

Optionally, a radiant heater 17 is arranged in the process chamber 3, which is used to heat the applied building material 15. As a radiant heater 17, an infrared heater can be provided for example.

The laser sintering device 1 also contains an exposure device 20 with a laser 21 which generates a laser beam 22 which is deflected via a deflection device 23 and through a focusing device 24 via a coupling window 25 which is attached to the upper side of the process chamber 3 in the chamber wall 4 , is focused on working level 7.

The laser sintering device 1 also contains a control unit 29, via which the individual components of the device 1 are controlled in a coordinated manner in order to carry out the construction process. Alternatively, the control unit can also be attached partially or entirely outside the device. The control unit can contain a CPU, the operation of which is controlled by a computer program (software). The computer program can be stored separately from the device on a storage medium from which it can be loaded into the device, in particular into the control unit. A powdery material is preferably used as the construction material 15, the invention being directed in particular to construction materials which form metal condensates. In terms of an oxidation reaction and thus a fire hazard, these include in particular iron and / or titanium-containing construction materials, but also copper, magnesium, aluminum, tungsten, cobalt, chromium and / or nickel-containing materials, as well as materials containing such elements Links.

In operation, in order to apply a powder layer, the carrier 10 is first lowered by a height which corresponds to the desired layer thickness. The applicator 16 first drives to the storage container 14 and takes from it a sufficient amount of the building material 15 to apply a layer. Then he drives over the construction field 8, brings there powdery construction material 15 onto the construction base or an already existing powder layer and pulls it out to form a powder layer. The application takes place at least over the entire cross section of the object 2 to be produced, preferably over the entire construction field 8, that is to say the area delimited by the container wall 6. Optionally, the powdery building material 15 is heated to a working temperature by means of a radiant heater 17.

The cross section of the object 2 to be produced is then scanned by the laser beam 22, so that the powdery building material 15 is solidified at the points which correspond to the cross section of the object 2 to be produced. The powder grains are partially or completely melted at these points by means of the energy introduced by the radiation, so that they are connected to one another as a solid after cooling. These steps are repeated until the object 2 is completed and the process chamber 3 can be removed.

FIG. 2 shows a schematic, partially sectioned view of a filter device 100 for filtering and here also for post-treatment of particles 51 carried along in a process gas 50 of a device for the generative production of three-dimensional objects in connection with a device 1 according to FIG. 1 according to a first From embodiment of the present invention. The particles 51 and the process gas 50 carrying the particles are represented by the corresponding arrow. The process gas 50 carrying the particles 51 is released from the process chamber 3 via an outlet 53 into the feed line 52 of the process gas 50 to the filter chamber 40, for example sucked off. The filter chamber 40 has, in addition to an inlet for the feed 52 of the product process gas 50 and the particles 51 entrained therein have an inlet for an oxidizing agent 60, which is supplied via an oxidizing agent supply 62, for after-treatment, likewise shown as a corresponding arrow. The oxidizing agent feed 62 is aligned with the process gas 50 entrained by the particles 51 exiting from the feed 52, so that the oxidizing agent 60 can penetrate the particle environment of the particles 51 in the area of the initiation of the oxidation reaction described below. An energy input source 70 designed as a radiant heater is provided here as the means for initiating the oxidation reaction, which couples its heat radiation into the filter chamber 40 via a transparent area 42 and absorbs it to a large extent from the particles 51 entrained in the process gas 50, so that these are heated in a targeted manner . The supply of the oxidizing agent 60 into the particle environment of the particles 51, in combination with the particle temperature generated by the energy input source 70, leads to an oxidation reaction in which the particles 51 burn off in a controlled manner and / or are at least passivated in a guided oxidation reaction to the extent that their fire and the tendency to explode is sufficiently inhibited. The process gas 50 carrying the particles 51 or now particle residues is then discharged through the (temperature-resistant) filter 41, on which the particles 51 or particle residues remain in accordance with the filter characteristics. The filtered process gas can exit the filter 41 from a clean gas outlet 54 and z. B. can be fed back to a process via a process gas supply 31 (see, for example, FIG. 1).

The filter device 100 can also have a separator, not shown, so that particles 51 formed from unsolidified building material 13 are separated from the process gas 50 so that they are not fed to the aftertreatment.

In the embodiment according to FIG. 2, the oxidizing agent guide 62, the supply 52 of the process gas 50 and the energy input source 70 are arranged in such a way that the oxidation reaction is triggered by the energy input source 70 in the particle environment in which the oxidizing agent 60 reacts with the process gas carrying the particles 51 50 hits and thereby mixes the particle environment. Alternatively, the particles 51 entrained in the process gas 50 can also first be heated to a temperature which then leads to an oxidation reaction when the particles 51 come together with the oxidizing agent 60. Likewise, the energy input to initiate the oxidation reaction can only take place when the mixing of the particle environment with the oxidizing agent 60 has already taken place, provided that the oxide medium content is still sufficient. This relates to both a spatial and a temporal approach.

Furthermore, the filter device 100 in FIG. 2 has a controller 80 which controls the oxidizing agent feed 62 and thus the amount of oxidizing agent 60 fed to the filter chamber, for example via valves, the outlet 53 and thus the amount of process gas 50 and particles 51 entrained therein as well as the energy input source 70 can control. To regulate at least one of these devices, which can be controlled by the control 80, a process monitoring system 90 is provided, which monitors at least the oxidizing agent content, the amount of particles or the temperature in the filter chamber 40. The regulation is carried out via the controller 80, but can also be formed by a unit that is separate from this. The control 80 can also be included in the control unit 29 of the laser sintering device 1 or can be assigned to the filter device 100.

FIG. 3 is a schematic, partially sectioned view of a filter device 100 for filtering a process gas 50. The process gas 50 enters the filter device 100 through a dirty gas inlet (feed 52). The line shown as feed 52 comes from the suction of a process chamber (see, for example, FIG. 1). The incoming process gas 50 then flows through the filter chamber 40, which here has the shape of a funnel which opens into the particle collecting container 55. Larger particles bounce off the edge of the filter chamber 40 and fall directly into this particle collecting container 55; lighter particles are carried along with the process gas and filtered out of the process gas 50 by means of the permanent filter 41. Above the filters there are cleaning units 56 with tanks which can clean the filters 41 by means of cyclic pressure surges. Particles removed by the filters 41 fall into the particle collecting container 55. The filtered process gas exits the filter device 100 again from the clean gas outlet 54.

FIG. 4 is a schematic, sectional view of FIG. 3. The four permanent filters 41, which are designed as filter cartridges, and in the middle a tube which opens into the particle collecting container 55 and can be closed by a shut-off valve 55a are clearly visible to prevent particles from escaping when the particle collecting container 55 is replaced. FIG. 5 is a schematic, sectional side view of a filter chamber 40 of a filter device 100 for filtering in a process gas 50, as it is e.g. B. is shown in FIG. A special feature are the permanent filters 41, which are hollow cylinders here with a pleated filter material 58 (designed in folds 59) (see also section AA). Both the pleating and the design as a hollow cylinder, each with an inner and an outer dirty gas side 57, contribute to an enlargement of the effective filter surface.

In this example, the filter device 100 includes an energy input source 70 for the left filter 41, to which the filter 41 is coupled. This energy input source 70 is used here to heat a metal fabric in the filter material 58, so that the filter 41 represents a heating element. This serves to bring about a controlled oxidation of the filtered particles. The heating effect can be achieved in that wires of the filter 41 are designed as (insulated) heating wires and the energy input source 70 supplies these wires with current.

FIG. 6 is a schematic, perspective illustration of a further preferred permanent filter 41. This is designed as a filter plate with an external dirty gas side. A process gas flow (not shown here) penetrates the filter 41 from the outside and particles are filtered out on the dirty gas side 57. The cleaned one

Process gas flow emerges from filter 41 against the arrows (above). For cleaning, an inert gas is blown into the filter in the direction of the arrows.

Finally, it is pointed out once again that the figures described in detail above are merely exemplary embodiments which can be modified in the most varied of ways by the person skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite article “a” or “an” does not exclude the possibility that the relevant characteristics can also be present more than once. Likewise, the term “unit” does not exclude that it consists of several interacting sub-components, which may also be spatially distributed. List of reference symbols

1 laser melting device

2 object / component

3 process chamber

4 chamber wall

5 containers

6 container wall

7 working level

8 construction site

10 carriers

11 base plate

12 build platform

13 Construction material

14 storage container

15 Construction material

16 coaters

17 Radiant heating

20 Irradiation device / exposure device

21 lasers

22 laser beam

23 Deflection device / scanner

24 Focusing Device

25 coupling window 29 control unit

31 Process gas supply

40 filter chamber

41 Filters / permanent filters

42 transparent area

50 process gas

51 particles

52 Feeder

53 outlet

54 Clean gas outlet

55 Particle collector 55a Butterfly valve 56 Cleaning unit

57 dirty gas side

58 filter material

59 fold 60 oxidizer

62 Oxidizing agent supply 70 Energy input source 80 Control 90 Process monitoring 100 Filter device

H horizontal direction V vertical direction

Claims

1. Filter device (100) for an additive manufacturing device (1) for purifying a process gas (50) of the additive manufacturing device (1), wherein the filter device (100) for purifying a volume of process gas (50) during operation has at least one permanent filter (41) comprises, and wherein the permanent filter (41) is designed to be temperature-resistant so that a temperature resistance of the permanent filter (41) is higher than 110 ° C during operation.

2. Filter device according to claim 1, wherein the permanent filter (41) is constantly designed so that a temperature resistance of the permanent filter (41) is higher than 150 ° C, preferably higher than 250 ° C, preferably higher than 350 ° C, particularly preferably higher than 500 ° C.

3. Filter device according to one of the preceding claims, wherein the permanent filter (41) comprises a metal filter and / or a ceramic filter and / or a glass wool filter, preferably wherein a metal filter is formed from at least one corrosion-resistant steel and / or from a nickel-based alloy and / or of copper and / or of mixtures or alloys thereof.

4. Filter device according to one of the preceding claims, wherein a mesh size of a filter material (58) of the permanent filter (41) is not more than 30 pm, preferably not more than 20 pm, preferably not more than 8 pm and / or at least 0.5 pm, preferably at least 1 pm, preferably at least 2 pm, particularly preferably 3 pm

5. Filter device according to one of the preceding claims, wherein the Perma nentfilter (41) comprises a support structure which is designed to support a filter surface of the permanent filter, to keep it in shape and / or to increase the mechanical strength of the permanent filter, preferably wherein the Support structure runs parallel to a filter material of the permanent filter, preferably at least in a partial area on whose dirty gas side (57) and / or on whose clean gas side or is integrated in the permanent filter (41).

6. Filter device according to one of the preceding claims, wherein a diam water of fibers and / or wires, which a filter material (58) of the permanent filter (41) form, is less than 20 pm, preferably less than 15 pm, preferably less than 10 pm, particularly preferably 5 pm, preferably, with a diameter of wires that form a support structure having a thickness of more than 100 pm, preferably less than 1000 pm.

7. Filter device according to one of the preceding claims, wherein a dirty gas side (57) of the Perma nentfilters (41) coming into contact with the process gas (50) to be purified has at least partially a, preferably meander-like, pleated surface, preferably to form a pleated surface A number of folds is arranged in the surface on the dirty gas side (57), the folds for pleating being particularly preferably folds in a continuous Ge fabric or being welded and / or glued to one another.

8. Filter device according to one of the preceding claims, wherein the permanent filter (41) is arranged in the filter device (100) that a dirty gas side (57) coming into contact with the process gas (50) to be purified is an outer surface of the permanent filter (41) and / or wherein the permanent filter (41) is arranged in the filter device (100) such that a dirty gas side (57) coming into contact with the process gas (50) to be purified is an inner surface of the permanent filter (41).

9. Filter device according to one of the preceding claims, wherein the permanent filter (41) is designed so that an oxidation reaction of the particles present in the permanent filter (41) can be initiated, the permanent filter (41) preferably being coupled to an energy input source (70) , and preferably a metal mesh, or part of a metal mesh of the permanent filter (41) represent a heating element.

10. Additive manufacturing device for manufacturing a component in an additive manufacturing process with a process room (3), a feed device for introducing a building material (15) into the process room (3) in layers, an irradiation unit (20) for the selective solidification of building material (15) in the process room (3) and with a filter device (100) according to one of the preceding claims 1 to 9 for purifying a process gas (50) of the additive manufacturing device (1).

11. A method for additive manufacturing of a component in an additive manufacturing process by means of an additive manufacturing device (1), the method comprising at least the following steps: - Introducing at least one layer of a building material (15) into a process space (3) of the manufacturing device (1),

- Selective solidification of the building material (15) in the process space (3) by means of a radiation unit (20) and - Purification of a volume of a process gas (50) of the additive manufacturing device (1) by means of a filter device (100) according to one of the preceding claims 1 to 9.

12. The method for additive manufacturing according to claim 11, wherein the purification of process gas (50) at a process gas temperature of more than 40 ° C, preferably at a process gas temperature of more than 110 ° C, preferably at a process gas temperature of more than 150 ° C , preferably at a process gas temperature of more than 200 ° C, particularly preferably at a process gas temperature of more than 250 ° C, particularly preferably at a process gas temperature of more than 300 ° C.

13. The method for additive manufacturing according to one of the preceding claims 11 or 12, wherein the permanent filter (41) is cleaned as a function of a differential pressure value of process gas (50) and wherein a differential pressure value at least 10 mbar, preferably at least 20 mbar, is preferred is at least 30 mbar, particularly preferably at least 40 mbar and / or wherein a cleaning pressure surge for cleaning the permanent filter (41) is preferably more than 3 bar, in particular more than 4 bar and / or preferably less than 5 bar.

14. The method for additive manufacturing according to one of the preceding claims 11 to 13, wherein a purification of process gas (50) and / or a cleaning of the permanent filter (41) takes place in such a way that particles removed from the permanent filter (41) are used as building material (15 ) can be used in an additive manufacturing process.

15. A method for additive manufacturing according to one of the preceding claims 11 to 14, wherein the permanent filter (41) is cleaned during the additive manufacturing process, in particular without interrupting the manufacturing process.