Device for the post-treatment of particles carried in a process gas

Abstract

Post-treatment device (100, 200, 300) for the post-treatment of particles (51) carried in a process gas (50) of a device for the additive manufacturing of three-dimensional objects, wherein the post-treatment device (100, 200, 300) comprises an oxidizing agent supply (62, 621, 622) for supplying oxidizing agent (60) to the particles (51) to initiate an oxidation reaction of the particles (51) with the oxidizing agent (60), and wherein a pre-separator is provided for separating particles, in particular unsolidified components of a building material, before the oxidation reaction.

Description

[0001] The present invention relates to a device for the post-treatment of particles carried in a process gas of a device for the additive manufacturing of three-dimensional objects.

[0002] Devices and processes for the additive manufacturing of three-dimensional objects are used, for example, in rapid prototyping, rapid tooling, or additive manufacturing. One example of such a process is known as selective laser sintering or laser melting. In this process, a thin layer of powdered build material is repeatedly applied, and the build material in each layer is selectively solidified by irradiating corresponding areas of the cross-section of the object to be manufactured with a laser beam.

[0003] During the production of three-dimensional objects, particles, particularly metal condensates when metallic materials are used, are carried along in the process gas discharged from the process chamber. These particles are sometimes highly reactive and react at high temperatures, releasing significant heat. This can lead to uncontrolled filter fires or dust explosions, especially in the area of ​​filters where the particles accumulate. This risk is increased when, for example, a filter chamber is opened to change the filter(s), as the increased airflow raises the probability of a reaction.

[0004] EP 1 527 807 proposes inerting the dust components from an explosive dust-air mixture using additive particles loaded onto filter plates. The quantity of additive particles is selected so that the mixture of these particles with the introduced dust does not constitute a flammable mixture, at least until the dust container reaches its upper fill level. Calcium carbonate and silicon dioxide particles are mentioned as additive particles in connection with aluminum dust. While the use of additional particles necessitates their provision, it also results in the dust container reaching its upper fill level more quickly, thus requiring more frequent emptying.

[0005] The object of the present invention is to provide an alternative or improved device for the post-treatment of particles, in particular metal condensates, carried in a process gas of a device for the additive manufacturing of three-dimensional objects, in which the risk of uncontrolled particle combustion is minimized.

[0006] This problem is solved by a post-treatment device according to claim 1, as well as a post-treatment device according to claim 11. Further developments of the invention are specified in the dependent claims. The post-treatment devices may also be further developed by the features of the method disclosed in the present application listed below.

[0007] In the inventive method for the post-treatment of particles carried in a process gas of a device for the additive manufacturing of three-dimensional objects, wherein the particles are fed to a filter chamber, an oxidizing agent is supplied to the particles and an oxidation reaction of the particles with the oxidizing agent is initiated.

[0008] In this context, process gas refers to the gas discharged, particularly extracted, from a process chamber, which, depending on the manufacturing process, may also be or comprise an inert gas. The process gas may contain both unsolidified components of a build material and process byproducts, such as condensates, for example, metal condensates. Such components carried in the process gas are collectively referred to as "particles," and it is preferred that the unsolidified components of the build material are not, or only in smaller quantities than those contained in the process gas upon exiting the process chamber, introduced into the post-treatment process according to the invention. This can be achieved, for example, using a cyclone separator that effectively separates the unsolidified components of the build material from the process byproducts, at least to a large extent.

[0009] In principle, "oxidation" within the scope of the invention is understood to mean a reaction according to the broad, commonly accepted chemical definition, i.e., a reaction involving the release of electrons by an electron donor and the acceptance of electrons by an electron acceptor. In the oxidation reaction, condensate particles preferably act as electron donors, releasing electrons to the oxidizing agent as the electron acceptor. In particular, the oxidation reaction is carried out by oxygen as the acceptor, for example, atmospheric oxygen or an alternative oxygen-containing carrier or reactive gas as the oxidizing agent. The form of oxygen is not limited to molecular oxygen, i.e., O₂, but also includes other forms such as ozone, i.e., O₃, or other elemental and / or molecular compounds containing oxygen atoms, whose oxygen content can be used as an oxidizing agent. Other oxidizing agents include, among others...Hydrogen peroxide H2O2 and its adducts such as sodium percarbonate, oxygen-containing anions (oxoanions) of transition metals in high oxidation states such as permanganate MnO. 4- or dichromate Cr2O7 2- and chromium(VI) oxide (Jones oxidation), metal ions such as Ce 4+ , precious metal ions such as those of silver and copper, anions of halogenated oxyacids such as bromate BrO3 - and hypochlorite ClO - Sulfur and the halogens fluorine, chlorine, bromine, and iodine are known to be involved. Through the oxidation reaction, the flammability or explosiveness of the particles is either sufficiently inhibited or the particles are selectively and thus controlled as they are "burned," i.e., reacted.

[0010] For the targeted oxidation reaction, this is preferably initiated by a change in the particle environment and / or a targeted energy input. For this purpose, for example, the oxidizing agent and / or the condensate particles and / or the unsolidified build material, as described later, and / or the particle environment can be heated to a predetermined temperature. Targeted heating of the particles, compared to heating the particle environment, reduces the temperature in the post-treatment device, thus preventing overheating. Alternatively or additionally, besides heating, for example by a tube heater, a heat exchanger, or convective heat transfer, other methods are also possible.An infrared heater, other forms of energy input to initiate or support the oxidation reaction, or to influence the oxidizing agent and / or the particles are possible, for example, by photochemical reaction with flash, plasma, electric arc, electrostatic discharges or eddy currents, catalysts for the atomic splitting of oxygen as an oxidizing agent, or by introducing activating agents to activate metal condensate surfaces or by electrolysis. Accordingly, the inventive method does not, in principle, prescribe a mandatory sequence for the steps of supplying the oxidizing agent and initiating an oxidation reaction. In other words, the initiation can also occur before the supply of the oxidizing agent or vice versa. The sequence of the process steps can result from the respective embodiments.It is equally possible to initiate the oxidation reaction solely by supplying the oxidizing agent, as well as by solely supplying energy from one of the above-mentioned energy input sources, whereby, in other words, only one of the above-mentioned process steps is sufficient by carrying out the process according to the invention in the sense of controlled process by-product oxidation.

[0011] It should be noted here that the initiation of an oxidation reaction according to the invention refers to the targeted initiation or support of an oxidation reaction. As long as the reactive particles are surrounded by oxidizing agents, such as oxygen components in the process gas carrying the particles or admixtures, through a supply of the process gas and an oxidizing agent supply through environments containing such components, for example because the supply of the process gas to the filter chamber or the filter chamber itself is not airtight or is flooded with gas containing such components, spontaneous oxidation can generally be assumed.This process, however, is primarily limited to passivation through the formation of oxide layers on the particles and only in a few cases, such as the aforementioned opening of the filter chamber and the resulting sudden increase in oxygen content, does it lead to exothermic oxidation reactions in the form of combustion. Such combustion then proceeds uncontrollably. The invention, however, focuses on controlled oxidation reactions that are triggered or supported by the targeted initiation of an oxidation reaction. The inventive method proceeds in a particularly controlled manner when the particles are surrounded by a largely inert atmosphere until the targeted initiation of an oxidation reaction or until the oxidizing agent is supplied and / or the aforementioned energy input is initiated, thus limiting or completely inhibiting the reaction of the particles.This can be achieved, for example, by ensuring that the process gas carrying the particles is itself an inert gas and that, either in the process gas supply and / or in the filter chamber, mixing with potentially contained oxidizing agents is largely avoided, except for the specifically added oxidizing agents, or that the process gas supply and / or the filter chamber itself contains inert gas, for example, by being flooded with it. If the process gas itself is not an inert gas, it can be mixed with inert gas in the supply and / or in the filter chamber to such an extent that a reaction of the particles with their particle environment is reduced or completely inhibited until the targeted addition of oxidizing agents.

[0012] The oxidation reaction need not be carried out on all particles, but can be limited to those particles that, due to their size or surface-to-volume ratio, their reaction properties, and / or their quantity, pose a corresponding fire or explosion risk. Furthermore, in connection with the input of energy to initiate the oxidation reaction, particularly with regard to heating, particle conglomerations or agglomerations, even sintering, can occur, thereby reducing the active surface area to a safe level. Such an effect can also be caused by the exothermic nature of the oxidation reaction.Preferably, as mentioned above, unconsolidated components of a build material can be pre-separated before the oxidation reaction, or preferably condensate particles from the particle environment carried in the process gas, for example by means of centrifugal separators, in order to be recycled, so that the oxidation reaction is thus essentially directed at the condensates as particles. These are often present, for example, as agglomerated particles with primary particle diameters in the range of 80 to 120 nm, or as primary particles in the range of 5 to 50 nm.

[0013] This eliminates the need for additive particles, for example. Furthermore, the general risk of fire and explosion can be reduced, preferably with no or only a minimal change in particle size, for instance, during combustion at moderate temperatures. Consequently, the risk of fire and explosion that may persist after filter replacement during disposal or other further processing of the filters and particles or particle residues is also reduced compared to filter replacement without prior treatment of the particles carried in the process gas.

[0014] Preferably, the supplied oxidizing agent is supplied to a particle environment, which is preferably provided in a flowable form, more preferably in a gaseous form, in particular in the form of an inert gas.

[0015] The free-flowing particle environment promotes the uniform distribution of the oxidizing agent within the particle environment. Providing a particle environment in gaseous form allows for the direct use of the process gas and is also advantageous for plant design with regard to the flow characteristics of gases. Furthermore, using an inert gas as the particle environment prevents or at least inhibits the reaction of its particles until a targeted oxidation reaction occurs.

[0016] The introduction of the oxidizing agent involves enriching the particle environment with an oxidizing agent, particularly in an area of ​​the intended oxidation reaction.

[0017] The particle environment can be formed by the process gas itself, which carries the particles, or by a medium contained in the process gas supply, the oxidant supply, and / or the filter chamber, or by a mixture thereof. Due to the fluidity of the particle environment, especially in gaseous form, the oxidant can be well distributed within it. For example, by including an inert gas as part of the particle environment, the reaction risk of the condensate particles and / or the proportions of unsolidified build material can be reduced by the inert environment until the oxidation reaction is deliberately initiated and / or the oxidant is deliberately added.

[0018] Preferably, the oxidizing agent is provided in a suitable state of matter, preferably in a flowable state, more preferably in a gaseous state, particularly in the form of oxygen. Depending on the oxidation reaction conditions, however, solids are also conceivable as oxidizing agents.

[0019] The term "suitable" refers to the purpose of oxidizing the particles or the particles to be subjected to the oxidation reaction, such that a largely complete oxidation reaction in this state of matter can be assumed for these particles. Here, too, the fluidity can, for example, facilitate the distribution of the oxidizing agent around the particles. In a gaseous particle environment, a gaseous oxidizing agent is particularly effective in achieving a uniform distribution.

[0020] The use of oxygen as an oxidizing agent is advantageous in many respects, such as its availability, especially with regard to the use of atmospheric oxygen, the high affinity of many particle materials for oxygen in the sense of oxidation reactions, or also in the sense of a targeted combustion.

[0021] Preferably, a volume fraction of the oxidizing agent, in particular oxygen, of at least 0.01 vol% and at most 20 vol%, preferably at least 1 vol%, particularly preferably at least 4 vol%, and / or preferably at most 10 vol%, particularly preferably at most 6 vol%, is supplied to the particles, based on the particle environment.

[0022] This can, for example, prevent an uncontrolled chain reaction and achieve explosion protection in accordance with ATEX regulations.

[0023] Preferably, the particles are heated, in particular to a temperature of at least 50 °C but not more than 650 °C, preferably at least 75 °C, more preferably at least 100 °C and / or preferably at most 200 °C, more preferably at most 150 °C.

[0024] Heating the particles can, for example, initiate or support an oxidation reaction. Heating can occur before, after, or even during the introduction of the oxidizing agent. The latter is particularly relevant if the point of introduction of the oxidizing agent is also intended as the site of the oxidation reaction, thus ensuring efficient heating. However, for various reasons, such as design requirements, heating can also occur before or after the introduction of the oxidizing agent.

[0025] As already mentioned, by directing the heating not to the gas surrounding the particles but to the particles themselves, overheating of the post-treatment device described later is avoided, especially during prolonged heating. For example, when using radiant heating, heat is absorbed primarily by the particles, and this heat absorption is insignificant compared to the amount of heat in the gas. Furthermore, it is also conceivable that the gas surrounding the particles could be recirculated and / or actively cooled. It should be noted here that the term "gas" in relation to the particle environment encompasses the process gas, a gaseous oxidizing agent, other gases present in the particle environment, and mixtures thereof, as this is not relevant to the particle heating itself but rather to the context of the oxidation reaction.

[0026] Depending on the material, the heating temperature can be advantageously set at comparatively higher values, such as around 200 °C for AlSi10Mg. In particular, the ignition temperature of the particles due to the heating process and / or the ignition temperature of the filter as a result of the heating may be exceeded, provided that the reaction takes place in the particle environment without filter contact and the upper limit of the filter's ignition temperature is again undercut before contact occurs. Less temperature-sensitive alternatives are metal or ceramic filters, for which the ignition temperature is higher.

[0027] Preferably, the oxidizing agent content surrounding the particles, in particular the oxygen content, and / or the temperature of the particle environment and / or the particles themselves are detected and influence the control of the oxidizing agent supply and / or a heating device and / or an extraction system.

[0028] The term "acquisition" is not limited to measuring the relevant values, but can also include deriving them from other information sources, such as parameter settings. However, measuring the values ​​can, for example, provide status information independent of the settings. Based on the acquired values ​​or a predetermined deviation from target values, influencing the control of the oxidizer supply and / or the heating device and / or the extraction system can involve switching off at least one of these components. In an advantageous embodiment, however, this influence corresponds to a control or readjustment to bring the process back within the predetermined range of the target values.Ultimately, depending on the degree of deviation and the associated risks, both intervention options can be provided for, for example, a regulation for deviations less than or equal to a predetermined deviation and shutdown when this deviation is exceeded.

[0029] The post-treatment device according to the invention for the post-treatment of particles carried in a process gas of a device for the additive manufacturing of three-dimensional objects, wherein the particles are fed to a filter chamber, comprises an oxidant supply for supplying oxidant to the particles and means for initiating an oxidation reaction of the particles with the oxidant.

[0030] The oxidant supply can be configured as a conduit that delivers an oxidant from an oxidant reservoir to the particles, or simply as an oxidant passage. The means for initiating an oxidation reaction can include, for example, means for supplying energy, particularly for increasing the temperature, or feeds or passages for supplying catalysts, surface activation agents, and / or electrolytes, as already comprehensively mentioned above.

[0031] As already explained in relation to the inventive method, the post-treatment device can, for example, achieve targeted oxidation of the particles in order to reduce the risk of fire and explosion.

[0032] Preferably, the oxidizing agent supply is associated with the process gas supply and / or connected directly or indirectly to the filter chamber.

[0033] The process gas supply is understood as the supply of the process gas to the filter chamber. If the oxidizer supply is linked to the process gas supply, then, for example, multiple filter chambers can be supplied from a single oxidizer supply and a single process gas supply, as the oxidizer supply does not need to be provided for each chamber individually. Conversely, if there is one filter chamber and multiple process gas supplies, then an oxidizer supply connected to the filter chamber can be advantageous. To increase flexibility, an optional connection or allocation method is also conceivable. The connection to the filter chamber does not necessarily have to be direct, but can also be indirect, for example, via functional intermediate sections such as valve sections.

[0034] Furthermore, by connecting the oxidant supply to the process gas supply, the targeted oxidation reaction of the particles can, for example, begin before the particles reach the filter chamber. Conversely, if the oxidant supply is connected to the filter chamber, a targeted oxidation reaction can be limited to the area within the filter chamber.

[0035] Preferably, the supply of oxidizing agent is directed essentially towards at least one filter in the filter chamber.

[0036] This allows, for example, the particles reaching at least one filter to be subjected to an oxidation reaction, or for the oxidation reaction to take place within the filter area, thus promoting the deposition of oxidized particles on the filter. Particularly with regard to the filter configuration with an energy input source described later, directing the oxidizing agent supply to the filter within the filter chamber proves advantageous.

[0037] Preferably, a control system, in particular a regulation system, is provided which controls the supply of oxidizing agent in such a way that it is supplied continuously, periodically or variably.

[0038] A continuous supply of the oxidizing agent can ensure a minimum oxidizing agent concentration. However, it can also be advantageous, for example, to initially withhold the oxidizing agent after initiating the reaction and allow the reaction to proceed with the amount supplied up to that point. A variable supply, meaning an event- or condition-dependent supply, is advantageous in many cases, particularly with regard to consumption and process control in the presence of fire and explosion hazards. With a periodic or variable supply, the control system can, for example, inhibit or block the supply of the process gas, such as by shutting off an exhaust system or by using appropriate shut-off devices. This makes it possible to conduct the oxidation reaction in a virtually closed system.In particular, devices designed to prevent feedback to the process chamber, preferably implemented using sealing elements, can prevent an undesired oxidation reaction extending into the process chamber. Such inhibition or blockage need not be contingent on preventing any additional particles carried in the process gas from entering the oxidation reaction, but can also, for example in the case of post-oxidation, suspend any further supply of process gas that would influence the oxidation process, even without particles. If an inert gas is used as the process gas, it could otherwise, for instance, reduce the oxidizing capacity.

[0039] Preferably, the post-treatment device has at least one energy input source, the energy input of which comes from outside the filter chamber, in particular through a radiation-transparent area into an interior of the filter chamber, and / or within the filter chamber, in particular through an energy input element integrated into the at least one filter.

[0040] The energy input source supplies energy to the oxidizing agent and / or the particles and / or the particle environment to initiate the oxidation reaction. For example, activation energy is supplied to the particles and / or energy is supplied to increase the temperature, thus increasing the likelihood that the particles themselves will provide the activation energy.

[0041] In an arrangement outside the filter chamber, the energy input can be directed onto the particles via a radiation-transparent area, for example, without further components or media heating up to essentially negligible absorption phenomena.

[0042] Alternatively or additionally, an arrangement within the filter chamber, in particular an energy input element integrated into at least one filter, can offer the advantage of introducing the energy input in a more targeted local manner.

[0043] However, an energy input source is also conceivable, the energy input of which comes from outside the supply of the process gas, in particular through a radiation-transparent area into an interior of the supply of the process gas, and / or within the supply of the process gas.

[0044] An energy input source associated with the process gas supply can be easily retrofitted by inserting an intermediate piece, for example as a retrofit kit, into the process gas supply. This intermediate piece encompasses the energy input source within or outside the gas supply and / or has a radiation-transparent area. Such an intermediate piece or connector can be attached as a connector. In addition to the energy input source, the corresponding intermediate or connector can also include an inlet for the oxidizer supply. Alternatively or additionally, the intermediate or connector can incorporate sensors for process monitoring.

[0045] Preferably, the at least one energy input source is preferably designed as a heating device and is preferably controllable and / or regulating via the control system, in particular the regulation system.

[0046] The term "heating device" refers to a device that enables the heating of the oxidizing agent, the particles, and / or the particle environment. Such a heating device can be used to initiate an oxidation reaction by providing activation energy, as well as to facilitate temperature-dependent oxidation processes. Furthermore, it can also support particle conglomeration, agglomeration, and / or sintering, for example, by providing a predetermined temperature level. By connecting to the control system, a temperature profile can be defined, tailored to the various mechanisms of action. Similarly, the heating device can also be integrated into a control system to react to deviations from the control parameters or to operate according to them.

[0047] The control system can initiate an oxidation reaction periodically at predetermined intervals via the energy input source or, more generally, the means of initiating the oxidation reaction. Alternatively, it can be event-driven, such as upon reaching a predetermined particle quantity, or upon request from an operator, for example, before opening the filter chamber. Regarding the latter example, it can also be stipulated that the filter chamber can only be opened after an oxidation reaction has been initiated and its completion can be assumed, or after process monitoring confirms this. This could be triggered by a specific particle quantity detected in the filter chamber before the oxidation reaction, or by a residual quantity detected afterward, which would then trigger the release condition.

[0048] Preferably, process monitoring is provided that monitors the oxidizing agent content, in particular the oxygen content, and / or the temperature.

[0049] Process monitoring can be used, for example, to record process states, output critical process states in the form of signal information or warning messages, trigger shutdowns, and / or, as part of a control system, transmit actual values ​​to the control system. The sensors used for process monitoring to measure oxidizer content or temperature are not limited to these parameters. Alternatively or additionally, the quantity of particles carried in the process gas can also be monitored.

[0050] As a process monitoring device, the process monitoring system can form its own independent unit, or the acquisition of monitored variables can be carried out by individual sensors that are combined into a process monitoring system, for example, in the control system. The acquisition of the monitored variables is preferably spatially resolved in the sense of determining a value within a region of interest, or at least such that the acquired variable allows for inferences to be made about the monitored variable within a region of interest.

[0051] Preferably, the control system, based on process monitoring, controls the oxidizing agent supply and / or the heating device and / or an extraction system.

[0052] In response to values ​​detected by process monitoring, for example, if an excessively low oxidant concentration is detected, the oxidant supply can be increased, the temperature raised, and / or the extraction, and thus the supply of process gas, throttled. The control of the process gas supply can be directed either at the quantity of particles carried in the process gas or at the quantity of process gas carrying the particles, which in turn influences the oxidant concentration during supply. Process monitoring and control thus form a closed-loop control system.

[0053] The filter according to the invention for use in a method or device according to the invention comprises a heating device which is designed as a resistance heater, in particular wire mesh and / or heating wire.

[0054] By designing the heating device as a resistance heater, a simple implementation is possible. A wire mesh is particularly suitable, which can be configured as a grid, net, or irregular structure. An irregular structure can, for example, exhibit different temperature ranges depending on the local density of the structure. The wire mesh or heating wire can be embedded in the filter fabric.

[0055] Because the filter incorporates the heating element, retrofitting conventional filter chambers into a post-treatment device or applying the post-treatment process is simplified. Alternatively or additionally, the filter can also be designed to provide the oxidizing agent or other means for initiating an oxidation reaction. For example, to provide the oxidizing agent, the filter can be made of or include materials that act as electron acceptors. Besides the heating element, the filter can also act as a catalyst for initiating an oxidation reaction or support the formation of activation surfaces.

[0056] Initiating the oxidation reaction at or within the filter area can also be advantageous because this is where the largest particle accumulations are expected. Here, an oxidation reaction can be triggered periodically or upon reaching a critical quantity before the filter chamber is opened, particularly within the framework of process monitoring or control based on the determined boundary conditions.

[0057] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the accompanying drawings. Fig. Figure 1 is a schematic, partially sectioned view of a device for the additive manufacturing of a three-dimensional object. Fig. Figure 2 is a schematic, partially sectional view of a post-treatment device for the post-treatment of particles carried in a process gas of a device for the additive manufacturing of three-dimensional objects in conjunction with a device according to Fig. 1 according to a first embodiment of the present invention, in which, in one embodiment, the oxidizing agent supply and the means for initiating the oxidation reaction can be assigned to the filter chamber. Fig. Figure 3 is a schematic, partially sectional view of a post-treatment device for the post-treatment of particles carried in a process gas of a device for the additive manufacturing of three-dimensional objects in conjunction with a device according to Fig. 1 according to a second embodiment of the present invention, in which, in one embodiment, the supply of the oxidizing agent and the means for initiating the oxidation reaction can be assigned to the supply of the process gas. Fig. Figure 4 is a schematic, partially sectional view of a post-treatment device for the post-treatment of particles carried in a process gas of a device for the additive manufacturing of three-dimensional objects in conjunction with a device according to Fig. 1 according to a third embodiment of the present invention, in which in one embodiment the oxidizing agent supply is directed towards the filter and the filter comprises the means for initiating the oxidation reaction.

[0058] The following refers to Fig. 1. A device for the additive manufacturing of a three-dimensional object is described. The in Fig. The device shown in Figure 1 is a laser sintering or laser melting device. 1. For building up an object 2, it contains a process chamber 3 with a chamber wall 4.

[0059] In process chamber 3, an upwardly open container 5 with a container wall 6 is arranged. The upper opening of the container 5 defines a working plane 7, the area within the opening of the working plane 7, which can be used to construct the object 2, being referred to as the building area 8. Process chamber 3 also includes a process gas supply 31 and an outlet 53 for process gas.

[0060] A support 10, movable in a vertical direction V, is arranged in the container 5. A base plate 11 is attached to the support plate, forming the bottom of the container 5. The base plate 11 can be a separate plate attached to the support 10, or it can be integral with the support 10. Depending on the powder used and the process, a build platform 12 can be attached to the base plate 11 as a base on which the object 2 is built. Alternatively, the object 2 can be built directly on the base plate 11, which then serves as the build platform. Fig. 1 is the object 2 to be formed in the container 5 on the construction platform 12 below the working level 7, shown in an intermediate state with several solidified layers, surrounded by unsolidified building material 13.

[0061] The laser sintering device 1 further comprises a storage container 14 for a powdered build material 15 that can be solidified by electromagnetic radiation and a coater 16 movable in a horizontal direction H for applying the build material 15 within the build area 8. Preferably, the coater 16 extends transversely to its direction of movement over the entire area to be coated.

[0062] Optionally, a radiant heater 17 is arranged in the process chamber 3, which serves to heat the applied build-up material 15. For example, an infrared radiator can be provided as the radiant heater 17.

[0063] The laser sintering device 1 further includes an exposure device 20 with a laser 21 which generates a laser beam 22 which is deflected via a deflecting device 23 and focused by a focusing device 24 via a coupling window 25 which is attached to the top of the process chamber 3 in the chamber wall 4 onto the working plane 7.

[0064] Furthermore, the laser sintering device 1 includes a control unit 29, which coordinates the control of the individual components of the device 1 to carry out the build process. Alternatively, the control unit can also be located partially or completely outside the device. The control unit can contain a CPU whose operation 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.

[0065] The build-up material 15 is preferably a powdered material, the invention being directed in particular to build-up materials forming metal condensates. In the sense of an oxidation reaction, this includes in particular iron- and / or titanium-containing build-up materials, but also copper-, magnesium-, aluminum-, tungsten-, cobalt-, chromium-, and / or nickel-containing materials, as well as compounds containing such elements.

[0066] In operation, to apply a powder layer, the carrier 10 is first lowered to a height corresponding to the desired layer thickness. The coater 16 first moves to the storage container 14 and takes from it a sufficient quantity of the build material 15 to apply one layer. It then moves over the build area 8, applies powdered build material 15 to the build substrate or a previously existing powder layer, and draws it out into 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 build area 8, i.e., the area bounded by the container wall 6. Optionally, the powdered build material 15 is heated to a working temperature by means of a radiant heater 17.

[0067] The cross-section of the object 2 to be produced is then scanned by the laser beam 22, causing the powdered build-up material 15 to solidify at the points corresponding to the cross-section of the object 2. The energy introduced by the radiation partially or completely melts the powder grains at these points, so that after cooling they are bonded together as a solid. These steps are repeated until the object 2 is complete and can be removed from the process chamber 3.

[0068] Fig. 2 A schematic, partially sectional view of a post-treatment device 100 for the post-treatment of particles 51 carried in a process gas 50 of a device for the additive manufacturing of three-dimensional objects in conjunction with a device 1 according to Fig. 1 according to a first 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 discharged from the process chamber 3 via an outlet 53 into the supply 52 of the process gas 50 to the filter chamber 40, for example by extraction. The filter chamber 40 has, in addition to an inlet for the supply 52 of the process gas 50 and the particles 51 carried therein, an inlet for an oxidizing agent 60 supplied via an oxidizing agent supply 62, also represented by the corresponding arrow. The oxidizing agent supply 62 is oriented towards the process gas 50 carrying the particles 51 exiting the supply 52 such that the oxidizing agent 60 can penetrate the particle environment of the particles 51 in the region of the initiation of the oxidation reaction described below.To initiate the oxidation reaction, an energy input source 70 designed as a radiant heater is provided. This source couples its thermal radiation into the filter chamber 40 via a transparent area 42 and is largely absorbed by the particles 51 carried in the process gas 50, thus selectively heating them. The introduction 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 and / or are at least passivated in a controlled oxidation reaction to such an extent that their flammability and explosive potential are sufficiently inhibited. The process gas 50, carrying the particles 51 or now particle residues, is then discharged through the filter 41, where the particles 51 or particle residues remain according to the filter characteristics.

[0069] The post-treatment device can also have a separator (not shown) so that particles 51 formed from unsolidified build material 13 are separated from the process gas 50, so that they are not fed to the post-treatment.

[0070] In the embodiment according to Fig. In Figure 2, the oxidant supply 62, the process gas supply 52, and the energy input source 70 are arranged such that the oxidation reaction is initiated by the energy input source 70 in the particle environment, where the oxidant 60 encounters the process gas 50 carrying the particles 51 and thereby mixes the particle environment. Alternatively, the particles 51 carried in the process gas 50 can first be heated to a temperature that, upon contact of the particles 51 with the oxidant 60, initiates an oxidation reaction. Likewise, the energy input to initiate the oxidation reaction can only occur after the mixing of the particle environment with the oxidant 60 has already taken place, provided that the oxidant concentration is still sufficient. This applies to both spatial and temporal considerations.

[0071] Furthermore, the post-treatment device features Fig. 2. A control unit 80 is provided, which can control the oxidant supply 62 and thus the quantity of oxidant 60 supplied to the filter chamber, for example via valves, the outlet 53 and thus the quantity of process gas 50 and particles 51 carried therein, as well as the energy input source 70. To control at least one of these devices, which can be controlled by the control unit 80, a process monitoring system 90 is provided, which monitors at least the oxidant content, the particle quantity, or the temperature in the filter chamber 40, in particular with spatial resolution, via one or more sensors, such as the sensors 91 and 92, which are shown by way of example. Fig. 3, and which can be included in process monitoring 90, are monitored. Control is carried out via the controller 80, but can also be provided by a separate unit. The controller 80 can also be included in the control unit 29 of the laser sintering device 1 or assigned to the post-treatment device 100.

[0072] In contrast to the in Fig. The first embodiment shown in 2 is in the Fig. In a second embodiment of the post-treatment device 200 shown in Figure 3, the oxidizer supply 621 and the energy input source, designed as a radiant heater 71, are assigned to the supply 521 of the process gas 50 and the particles 51 carried therein. The supply 521 comprises a supply section 5211 facing the process chamber 3, a supply section 5212 facing the filter chamber 40, and an intermediate section 5213. The oxidizer supply 621 feeds the oxidizer 60 to the process gas 50, which carries the particles 51, in the supply section 5211 facing the process chamber 3. Alternatively, the supply can also be provided in the intermediate section 5213, in particular upstream of the radiant heater 71 acting in the intermediate section 5213, or in the supply section 5212 facing the filter chamber 40.The intermediate section 5213 is designed to be inserted between the feed section 5211 facing process chamber 3 and the feed section 5212 facing filter chamber 40. Accordingly, the intermediate section 5213 can be a retrofit kit that easily enables the adaptation of conventional systems into a post-treatment device for the post-treatment of particles carried in a process gas 50. The intermediate section 5213 has a circumferential, radiation-transparent area 524 through which the energy of an energy input source 71, also rotating around a longitudinal axis of the intermediate section 5213, is coupled into the intermediate section 5213.

[0073] In the post-treatment device 200 after Fig. In the feed section 5211 facing process chamber 3, the oxidizing agent 60 is first supplied to the process gas 50, which carries the particles 51, via the oxidizing agent supply 621, so that the particle environment of the particles 51 carried in the process gas 50 is permeated with the oxidizing agent 60. The mixture of the process gas 50 carrying the particles 51 and the oxidizing agent 60 passes through the intermediate section 5213, in which the oxidation reaction is initiated via the energy input source 71. For process monitoring and the control based thereon via the controller 80, a sensor 91 is provided in the feed section 5211 facing process chamber 3 to detect the quantity of particles 51 carried in the process gas 50, and a sensor unit 92 is provided in the intermediate section 5213 to measure the temperature and the oxidizing agent content.

[0074] In the Fig.In the fourth embodiment of the post-treatment device 300, as shown in Figure 4, the oxidizing agent supply 622 is connected to the filter chamber 40 such that it is directed essentially towards the filter 41, and thus the oxidizing agent 60 flows around the filter 41 or permeates the filter 41. This allows the oxidizing agent 60 to be efficiently supplied to the particles 51 carried in the process gas 50 at the filter 41. Particularly in the case of a targeted oxidation reaction that is not intended to be continuous, the largest accumulation of particles 51 to be supplied for the targeted oxidation reaction is to be expected at the filter. In a further development, the filter 41 can also have a resistance heater in the form of a heating wire 72 incorporated into or surrounding the filter fabric, which serves as an energy input source to initiate the oxidation reaction.As already explained, the heat input via the heating wire can also be used to support an oxidation reaction initiated by other means. Furthermore, a process monitoring system 90 is provided, which can, for example, transmit information about the oxidant content, the temperature, and / or the quantity of particles 51 carried in the process gas 50 to the control unit 80.

[0075] In one application example, the process monitoring unit 90 detects the quantity of particles 51 supplied to the filter chamber 40 and / or the filter 41. When a predetermined quantity of particles 51 is reached, the oxidation reaction is initiated by adding the oxidizing agent 60 via the heating wire 72. Preferably, the oxidation reaction is effected by the particles 51 burning off on the filter 41. Alternatively, in addition to the quantity of particles 51, a predetermined time interval can also be used as a criterion for initiating an oxidation reaction. Another alternative allows for a further triggering event, for example, by a signal from the operator before the filter chamber 40 is opened to remove the filter 41. The various alternatives are transferable to the other embodiments and can also be combined with each other.The supply of oxidizing agent 60 via oxidizing agent supply 622 can be controlled such that the filter chamber 40 receives the oxidizing agent 60 only when the oxidation reaction is initiated or intended to be initiated. Alternatively, the filter chamber 40 can be continuously supplied with at least a minimum level of oxidizing agent, or supplied in such a way that the minimum level is maintained within the filter chamber 40. In the first variant, an oxidation reaction with the oxidizing agent 60 is avoided as long as no initiation of the oxidation reaction is intended. In the second variant, for example, passivation of the particles 51 can be supported, so that the combustion resulting from the initiation of the oxidation reaction is directed at the particles 51 whose flammability and explosion susceptibility have not been sufficiently inhibited by passivation.Here too, a combination of the variants can be provided in the sense of a comparatively low constant oxidant content in the filter chamber 40 or at the filter 41 and an increase in the oxidant content at predetermined times, i.e. for example when a predetermined quantity of particles 51 is reached, after a predetermined period of time or on demand. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 1 527 807

[0004]

Claims

[1] Post-treatment device (100, 200, 300) for post-treatment of particles (51) carried in a process gas (50) of a device for the additive manufacturing of three-dimensional objects, wherein the post-treatment device (100, 200, 300) comprises an oxidizing agent supply (62, 621, 622) for supplying oxidizing agent (60) to the particles (51) to initiate an oxidation reaction of the particles (51) with the oxidizing agent (60), and wherein a pre-separator is provided for separating particles, in particular unsolidified components of a building material, before the oxidation reaction. [2] Post-treatment device according to claim 1, wherein the pre-separator is a cyclone separator or a centrifugal separator. [3] Post-treatment device according to claim 1 or 2, wherein the post-treatment device (100, 200, 300) is configured to initiate an oxidation reaction of the particles with the oxidizing agent solely by supplying the oxidizing agent, or wherein the post-treatment device (100, 200, 300) further comprises means for initiating an oxidation reaction of the particles (51) with the oxidizing agent (60). [4] Post-treatment device according to one of claims 1 to 3, wherein the post-treatment device has at least one energy input source (70, 71, 72), in particular a heating device, such as a tube heater, a heat exchanger, or an infrared heater, wherein heating preferably takes place during the supply of the oxidizing agent. [5] Post-treatment device according to one of claims 1 to 4, wherein the post-treatment device is configured to supply the supplied oxidizing agent (60) to a particle environment and / or is located in a particle environment which is provided in a flowable, preferably gaseous, state, and / or wherein the post-treatment device is configured to provide the oxidizing agent (60) in a flowable state of matter, preferably gaseous. [6] Post-treatment device according to any one of claims 1 to 5, wherein the oxidizing agent is oxygen, in particular atmospheric oxygen. [7] Post-treatment device according to one of claims 1 to 6, further comprising a process monitoring (90) which monitors the oxidizing agent content, in particular an oxygen content, and / or the particle quantity and / or the temperature, in particular by means of at least one sensor. [8] Post-treatment device according to one of claims 1 to 7, further comprising a control (80), in particular a control system, wherein the control system preferably controls the oxidizing agent supply in such a way that the oxidizing agent is supplied continuously, periodically or variably, and / or wherein the control system preferably controls the oxidizing agent supply (62, 621, 622) and / or the energy input source (70, 71, 72) and / or an outlet (53), in particular on the basis of process monitoring (90). [9] Post-treatment device according to one of claims 1 to 8, wherein the oxidizing agent supply is designed as a line for supplying an oxidizing agent from an oxidizing agent storage, or wherein the oxidizing agent supply is designed as an oxidizing agent passage. [10] Post-treatment device according to any one of claims 1 to 9, wherein the particles (51) carried by the process gas (50) of the device for additive manufacturing of three-dimensional objects comprise metal condensates, and / or wherein a build-up material used in the device for additive manufacturing of three-dimensional objects is a build-up material forming metal condensates, in particular an iron- and / or titanium-containing build-up material, and / or copper-, magnesium-, aluminium-, tungsten-, cobalt-, chromium-, and / or nickel-containing material, as well as compounds containing such elements. [11] Post-treatment device (100, 200, 300) for post-treating particles (51) carried in a process gas (50) of a device for additive manufacturing of three-dimensional objects, wherein the process gas is formed by the gas discharged from a process chamber (3) of the device (1) for additive manufacturing, wherein the post-treatment device (100, 200, 300) comprises an oxidant supply (62, 621, 622) for supplying oxidant (60) to the particles (51) to initiate an oxidation reaction of the particles (51) with the oxidant (60), wherein the oxidant supply is configured such that the supplied oxidant (60) is supplied to a particle environment and / or is located in a particle environment formed by the process gas.

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