Method and apparatus for post-treatment of particles carried in a process gas and filter therefor - Patents.com

Abstract

The present invention relates to a method for post-processing particles (51) transported in a process gas (50) in an apparatus (1) for the production and manufacturing of three-dimensional objects, in which the particles (51) are introduced into a filter chamber (40). An oxidizing agent (60) is added to the particles (51) to initiate an oxidation reaction of the particles (51) with the oxidizing agent (60).

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for post-treating particles carried in the process gas of an apparatus for producing three-dimensional objects, and a filter therefor. [Background technology]

[0002] Methods and apparatus for generative manufacturing of three-dimensional objects are used, for example, for rapid prototyping, rapid tooling, and additive manufacturing. One such method is known as "selective laser sintering or laser melting," in which thin layers of powdered build material are repeatedly applied and each layer of the build material is selectively solidified by selectively irradiating each layer with laser light at locations that correspond to the cross-section of the object to be built.

[0003] When manufacturing such three-dimensional objects, particles are carried in the process gases taken from the process chambers, especially when metallic building materials are used, which carry metal condensates that are partly highly reactive and react at high temperatures with high heat release. This can lead to uncontrolled fires or dust explosions in the filters, especially in the vicinity of the filters where the particles carried in the process gases accumulate. This risk is amplified, for example, when the corresponding filter chamber is opened to replace the filter, as the associated increase in air supply increases the possibility of reactions.

[0004] Patent document 1 proposes an inerting method for separating dust components from explosive dust-air mixtures using additive particles loaded into filter plates, where the amount of additive particles is selected so that a mixture of these particles with the introduced dust does not constitute a flammable mixture at least until the upper filling level of the dust container is reached. Calcium carbonate and silicon dioxide particles are described as additive particles for aluminum dust. However, the use of additional particles, in addition to providing them, allows a faster approach to the upper filling level, which makes it necessary to empty the dust container more frequently. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 1527807 Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present invention to provide an alternative or improved method and an alternative or improved device for the post-treatment of particles, in particular metal condensates, carried in the process gases of an apparatus for the production and manufacturing of three-dimensional objects, as well as a filter therefor, minimizing the risk of uncontrolled particle combustion. [Means for solving the problem]

[0007] This object is achieved by the method according to claim 1 and the method according to claim 14 The post-processing device according to claim 25 This is achieved by the filter according to claim 1. Further aspects of the invention are specified in each of the dependent claims, whereby the method may also be developed further with the apparatus features described below or in the dependent claims, or vice versa, or each apparatus feature may be used together with other features for further aspects.

[0008] According to the method of the present invention for post-treatment of particles transported in a process gas in an apparatus for the production and manufacturing of three-dimensional objects, the particles are led to a filter chamber, an oxidizing agent is added to the particles, and an oxidation reaction between the oxidizing agent and the particles is initiated.

[0009] In this context, treatment gas should be understood as the gas discharged from the treatment chamber, in particular the gas extracted, which may be or contain an inert gas depending on the production process. The treatment gas may contain both unsolidified components of the building material and process by-products such as condensates, for example metal condensates. Such components carried in the treatment gas are summarized under the term "particles". Here, it is preferred not to supply unsolidified components of the building material to the post-treatment method according to the invention, or to supply them in an amount less than that contained in the treatment gas when it leaves the treatment chamber. This can be achieved, for example, by means of a cyclone separator, which effectively separates the unsolidified components of the building material, at least to a large extent, from the process by-products.

[0010] Basically, "oxidation" in the context of the present invention is understood according to the general broad chemical definition, i.e. as a reaction involving the donation of electrons by an electron donor and the acceptance of electrons by an electron acceptor. In the oxidation reaction, the condensate particles as electron donors preferably donate electrons to an oxidant as an electron acceptor. In particular, the oxidation reaction is carried out with oxygen as the acceptor, e.g. atmospheric oxygen, or an alternative oxygen-containing carrier gas, or a reactive gas as the oxidant. The form of oxygen is not limited to molecular oxygen, i.e. O2, but also includes other forms, e.g. ozone, i.e. O3, or other elemental and / or molecular compounds containing oxygen atoms, whose oxygen component can be used as an oxidant. Other oxidants include, in particular, hydrogen peroxide H2O2 and its adducts, such as sodium percarbonate, permanganate MnO4, etc. - and chromate Cr2O7 2-Oxygen-containing anions (oxyanions) of transition metals in high oxidation states, such as chromium(VI) oxide (Jones oxidation), Ce 4+ metal ions such as silver ions and copper ions, and bromate BrO3 - and hypochlorite, ClO - and sulfur, and the halogen family of fluorine, chlorine, bromine, and iodine. The oxidation reaction at least sufficiently suppresses the fire or explosion tendency of the particle, or "burns" or reacts out the particle in a targeted and therefore controlled manner.

[0011] For targeted oxidation reactions, the oxidation reaction is preferably initiated, i.e., deliberately initiated, by a change in the particle environment and / or a targeted energy input. For this purpose, for example, the oxidant and / or the condensate particles and / or the unsolidified building material and / or the particle environment may be heated to a predetermined temperature, as described below. Targeted heating of the particles, for example, reduces the temperature in the post-treatment device to reduce overheating, compared to heating of the particle environment. Alternatively or additionally, in addition to heating, for example, by tube heaters, heat exchangers, convective heat transfer, or infrared radiant heaters, other forms of energy input are also possible to initiate or support the oxidation reaction or to affect the oxidant and / or particles, for example, by photochemical reaction with flash light, plasma, electric arc, electrostatic discharge or eddy current, catalyst for atomic decomposition of oxygen as an oxidant, etc., or by addition of an activator to activate the metal condensate surface, or by electrolysis. Thus, the inventive method according to the general concept of the invention does not essentially require a mandatory sequence of steps of supplying an oxidizing agent to initiate the oxidation reaction. In other words, initiation may occur before the addition of the oxidizing agent or vice versa. A sequence of process steps can be obtained from each embodiment. It is also possible to initiate the oxidation reaction only by supplying an oxidizing agent or only by supplying energy from one of the above energy sources. In other words, in the sense of a controlled oxidation of process by-products, by carrying out the inventive method, only one of the above method steps is sufficient.

[0012] Here, the initiation of the oxidation reaction according to the invention refers to the fact that the oxidation reaction is specifically initiated or supported. Natural oxidation can in principle be envisaged insofar as the reactive particles are surrounded by an oxidant, such as the oxygen component in the process gas or mixture carrying the particles, by the process gas supply and oxidant supply via an environment containing said component. This is because, for example, the supply of the process gas to the filter chamber or the filter chamber itself is not gas-tight or is filled with a gas containing said component. However, this is mainly limited to passivation by forming an oxide layer on the particles and only leads to an exothermic oxidation reaction in the sense of a burn-off in a few cases, such as the aforementioned opening of the filter chamber and the resulting sudden increase in the oxygen content supplied. However, such a burn-off proceeds in an uncontrolled manner. The invention, however, concerns a controlled oxidation reaction that is initiated or supported by a targeted initiation of the oxidation reaction. The method according to the invention proceeds in a particularly controlled manner if the particles are surrounded by a substantially inert atmosphere that limits or completely prevents the reaction of the particles until the targeted start of the oxidation reaction or until the supply of the oxidizing agent and / or until the start of the energy input. This is achieved, for example, in that the processing gas that transports the particles is itself an inert gas, and that mixing with the oxidizing agent potentially contained therein in the processing gas supply and / or in the filter chamber is avoided as far as possible, except for the oxidizing agent that is specifically added, or that the processing gas supply and / or the filter chamber itself contains an inert gas, for example is filled with an inert gas. If the processing gas itself is not an inert gas, the processing gas may be mixed with an inert gas in the supply and / or in the filter chamber to such an extent that the reaction of the particles with their particle environment is suppressed or completely prevented until the targeted addition of the oxidizing agent.

[0013] The oxidation reaction does not necessarily have to be effected on all particles, but may be limited to those particles that, depending on their size or surface area to volume ratio, their reactive properties, and / or the proportion of particles, cause a corresponding risk of combustion or explosion. In connection with the energy input to initiate the oxidation reaction, particularly with respect to heating, conglomeration or agglomeration of the particles up to sintering may occur, whereby the active surface may be reduced to a non-hazardous level. Such an effect may also occur by exothermic oxidation reactions. Preferably, as mentioned above, the unsolidified components of the building material may be separated before the oxidation reaction. Alternatively, preferably, the condensate particles may be separated, for example by a centrifuge, from the particle environment in which they are carried in the process gas and recycled, so that the oxidation reaction is substantially directed to the condensate as particles. They are often present, for example, as agglomerated particles with a primary particle size in the range of 80-120 nm, as primary particles in the range of 5-50 nm.

[0014] In this way, for example, the use of additive particles may be omitted. Furthermore, for example, in the case of a burn-off at a low temperature, the general risk of fire and explosion may be reduced, since there is preferably no or only a small change in particle size. In this respect, the risk of fire and explosion that still exists after filter replacement during disposal or other further processing of the filter and particles or residual particles is reduced compared to filter replacement without prior post-processing of the particles entrained in the processing gas.

[0015] Preferably, the oxidant supplied is provided to the particle environment, preferably provided in a flowable form, more preferably in gaseous form, especially in the form of an inert gas. The flowable particle environment aids in the uniform distribution of the oxidant in the particle environment. Providing a gaseous particle environment allows the direct use of process gases and also has advantages in terms of gas flow characteristics in terms of equipment design. Furthermore, by using an inert gas as the particle environment, reaction of the particles is prevented or at least inhibited until the targeted oxidation reaction occurs. In this regard, the addition of oxidizing agent enriches the particle environment with oxidizing agent, particularly in the area of ​​the intended oxidation reaction.

[0016] The particle environment may be formed by the process gas itself carrying the particles, or by the medium contained in the process gas supply and / or the oxidant supply and / or the filter chamber, or by a mixture thereof. Due to the flowability of the particle environment, the oxidant can be well distributed in the particle environment, especially in gaseous form. If an inert gas is provided as part of the particle environment, for example, the reaction risk of the condensate particles and / or the amount of unsolidified building material can be reduced by the inert environment until the oxidation reaction is initiated in a targeted manner and / or until the oxidant is added in a targeted manner. Preferably, the oxidizing agent is provided in a suitable state of matter, preferably flowable, more preferably gaseous, especially in the form of oxygen, however, solids are also possible as oxidizing agents, depending on the oxidation reaction conditions.

[0017] The term "suitable" relates to the purpose of the oxidation of the particles or particles fed to the oxidation reaction, where a substantially complete oxidation reaction in this state of matter is envisaged for these particles. Here, the fluidity can, for example, facilitate the distribution of the oxidant around the particles. In the case of a gaseous particle environment, a uniform distribution is particularly well achieved with a gaseous oxidant. The use of oxygen as an oxidizing agent seems appropriate in many respects, including its availability, particularly with respect to the use of atmospheric oxygen, and the high affinity of many particulate materials for oxygen, either in the sense of oxidation reactions or, alternatively, in the sense of explicitly intended burn-off. Preferably, an oxidizing agent, in particular oxygen, is added to the particles in a volume fraction of 0.01% by volume to 20% by volume, preferably 1% by volume or more, particularly preferably 4% by volume or more and / or preferably 10% by volume or less, particularly preferably 6% by volume or less, relative to the particle environment. In this way, for example, uncontrolled chain reactions can be prevented and explosion protection within the meaning of ATEX regulations can be achieved. Preferably, the particles are heated, in particular, to a temperature of 50°C to 650°C, preferably 75°C or more, more preferably 100°C or more, and / or preferably 200°C or less, more preferably 150°C or less.

[0018] The particles can be heated, for example, to initiate or support an oxidation reaction. Heating can occur before, after, or during the addition of the oxidizing agent, especially if the latter is intended to be the site of the oxidation reaction, and heating is efficient. Heating can also occur upstream or downstream of the addition of the oxidizing agent for various reasons, such as design considerations. As already mentioned, in that the heating is directed towards the particles and not towards the gas in the particle environment, overheating of the aftertreatment device described below is avoided, especially in the case of heating over long periods of time. For example, when using radiant heaters, heat is essentially only absorbed by the particles, which is not large compared to the amount of heat in the gas. Furthermore, it is in principle conceivable to recirculate and / or actively cool the gas in the particle environment. It should be noted in this respect that the term "gas" in relation to the particle environment also includes the process gas and the gaseous oxidant as well as other gases present in the particle environment and mixtures of these gases, since this is not relevant with respect to particle heating, but should be taken into account in terms of the oxidation reaction.

[0019] Depending on the material, the heating temperature can be relatively high, such as around 200° C. for AlSi10Mg. In particular, the heating may result in a heating and / or ignition temperature of the filter that exceeds the ignition temperature of the particles, provided that the reaction takes place in the particle environment without filter contact and that the upper ignition temperature falls again before filter contact. Temperature-insensitive options include metal or ceramic filters, which have higher ignition temperatures. Preferably, the oxidant content, in particular the oxygen content, surrounding the particle and / or the temperature of the particle environment and / or the particle itself is detected and influences the control of the oxidant supply and / or the heating device and / or the exhaust device.

[0020] The term "detection" is not limited to the measurement of the corresponding values, but may also include their derivation from other sources, such as parameter settings. The measurement of the values ​​may, however, for example, reflect setting-independent status information. The intervention affecting the control of the oxidant supply and / or the heating device and / or the exhaust device according to a detected value or a predefined deviation from a target value is to shut down at least one of these devices. In an advantageous further embodiment, however, the intervention corresponds to a closed-loop control or a readjustment control to bring the process back within a predefined range of the target value. However, finally, depending on the degree of deviation and the associated risk, both possibilities of intervention may be provided, for example control in case of deviations below a predefined deviation and shut down in case of deviations above this deviation.

[0021] The post-treatment device of the present invention is a post-treatment device for post-treatment of particles carried in the processing gas of a three-dimensional object generating and manufacturing device, and includes an oxidizer supply section for adding an oxidizer to the particles, in which the particles are supplied to a filter chamber, and a device for initiating an oxidation reaction of the particles with the oxidizer. The oxidant supply may be in the form of a conduit through which the oxidant can be supplied to the particles from the oxidant reservoir, or in the form of an oxidant passage only. The device for initiating the oxidation reaction may, for example, comprise a device for introducing energy, in particular energy for increasing the temperature, or inlets or ducts for adding catalysts, surfactants and / or electrolytes, as already mentioned comprehensively. As already mentioned with respect to the method according to the invention, the aftertreatment device can achieve selective oxidation of the particles, for example to reduce the risk of fire and explosion. Preferably, the oxidant supply is linked to a supply of process gas and / or is directly or indirectly connected to the filter chamber.

[0022] A supply of process gas is understood as a supply of process gas to the filter chamber. If the oxidizer supply is linked to the process gas supply, for example with one oxidizer supply and one process gas supply for a number of filter chambers, then it is not necessary to provide an oxidizer supply for each filter chamber, and these several filter chambers can be supplied. Conversely, for example with one filter chamber and several process gas supplies, an oxidizer supply connected to the filter chamber can be advantageous. For increased flexibility, optional connection or arrangement options are also conceivable. The connection to the filter chamber does not necessarily have to be direct, but may be provided indirectly, for example via a functional intermediate part, such as a valve part. Furthermore, by connecting an oxidizer supply to the process gas supply, targeted oxidation reactions of particles can occur, for example, before the particles reach the filter chamber. Conversely, if the oxidizer supply is connected to the filter chamber, the targeted oxidation reactions can be limited to the area of ​​the filter chamber. Preferably, the oxidant supply is essentially led to at least one filter in the filter chamber.

[0023] In this way it is achieved, for example, that the particles reaching the at least one filter are subjected to an oxidation reaction or that an oxidation reaction takes place in the region of the filter, with the result that oxidized particles are preferably deposited on the filter. In particular with regard to the embodiments described below for filters with an energy input source, an oxidizer supply direction towards the filter in the filter chamber proves to be advantageous. Preferably, a controller, in particular a closed loop controller, is provided that controls the oxidant supply to supply oxidant continuously, periodically or variably.

[0024] The continuous addition of oxidizing agent can provide a minimum oxidizing agent concentration. However, it is also advantageous, for example, at the beginning after the start of the oxidation reaction, not to further supply oxidizing agent and to allow the oxidation reaction to proceed with the amount supplied up to that point. Variable addition in the sense of event-dependent or state-dependent addition is often advantageous from the point of view of control, especially with regard to consumption values ​​and process control in the case of fire and explosion risks. In the sense of periodic or variable addition, the control unit can, for example, limit or cut off the supply of the process gas by shutting off the exhaust device for the supply or by a corresponding closing element. In this way, the oxidation reaction can be carried out in a quasi-closed system. In particular, in the case of a device for avoiding feedback to the process chamber, which can be preferably achieved by a closing element, it is possible to prevent undesired oxidation reactions from reaching the process chamber. Such a limit or cut off does not have to be related to the condition that no additional amount of particles carried in the process gas is introduced into the oxidation reaction, but, for example, in the case of after oxidation, further addition of the process gas that affects the oxidation process can be interrupted and thus also particle-free. If an inert gas is used as the process gas, this can, for example, reduce the oxidation capacity again in another way. Preferably, the aftertreatment device comprises at least one energy input source, the energy input being from outside the filter chamber, in particular via a radiation-transparent part inside the filter chamber, and / or from inside the filter chamber, in particular via an energy input element integrated in at least one filter.

[0025] The energy input source provides energy to the oxidant and / or the particle and / or the particle environment to initiate the oxidation reaction, for example, energy to increase the activation energy and / or temperature is provided to the particle to increase the likelihood that the activation energy is provided by the particle itself. When located outside the filter chamber, the energy input can be directed through the radiation transparent portion to the particles, for example, without heating any further components or media except for essentially negligible absorption phenomena. Alternatively or additionally, placement within the filter chamber, and in particular an energy input element integrated into at least one filter, may provide the advantage, for example, of introducing energy input in a more locally targeted manner. However, it is also conceivable to provide an energy input source for inputting energy from outside the process gas supply, in particular via a radiation transparent part into the interior of the process gas supply and / or from within the process gas supply.

[0026] In the case of an energy input source linked to a supply of process gas, the energy input source can also be easily added retrofit, for example by inserting an intermediate part, such as a retrofit kit with an internal or external energy input source and / or with a radiation transparent part, into the supply of process gas or by adding such an element as a connecting part. In addition to the energy input source, the corresponding intermediate or connecting part may also be equipped with an inlet for the addition of an oxidizing agent. Alternatively or additionally, the intermediate or connecting part includes a sensor for process monitoring. Preferably, the at least one energy input source is configured as a heating device and can preferably be controlled and / or regulated by a controller, in particular a closed loop controller.

[0027] The term "heating device" is understood to mean a device making it possible to heat the oxidizing agent, the particles and / or the particle environment. Such a heating device can be used as a device for initiating the oxidation reaction, in the sense of providing activation energy and of a temperature-dependent oxidation process. Furthermore, for example, agglomeration or cohesion and / or sintering of the particles can be assisted by providing a predetermined temperature level. By connection to a control unit, temperature profiles aimed at different operating mechanisms in each case can be predetermined. Likewise, the heating device can be integrated into a control loop so as to be able to react to values ​​that deviate from the control settings or to operate according to adjustment parameters. The control unit can provide for the initiation of the oxidation reaction via an energy input source or via a device for initiating the oxidation reaction periodically, typically at predefined time intervals, or event-dependent in the sense of feedback control, such as reaching a predefined amount of particles, or upon request by an operator, for example before opening the filter chamber. For the latter example, the filter chamber may only be opened if the oxidation reaction has been pre-initiated and presumed to have been completed or if the process monitoring has confirmed this. This confirmation is optionally made depending on the detected amount of particles in the filter chamber, in the sense of a residual amount before the oxidation reaction as a triggering condition or afterwards as a release condition. Preferably, process monitoring is provided, monitoring the oxidant content, especially the oxygen content, and / or the temperature.

[0028] Process monitoring can be used, for example, to record process conditions, to output critical process conditions in the form of signal information or warning messages, or to initiate a shutdown, and / or to pass actual values ​​to a closed loop control as part of a regulation process. Sensors measuring oxidant content and temperature used for process monitoring are not limited to detecting these values. Alternatively or additionally, the amount of particles entrained in the process gas can also be monitored. As a device for process monitoring, the process monitoring may form its own independent unit or the detection of the variables to be monitored may be carried out by individual sensors, which are combined to form a process monitoring unit, for example in the control unit. Preferably, the detection of the values ​​to be monitored must have a spatial resolution in the sense of determining the values ​​in the region of interest or at least such that conclusions can be drawn about the values ​​to be monitored in the region of interest via the detected values. Preferably, the controller controls the oxidant supply and / or the heating device and / or the exhaust based on the process monitoring.

[0029] In response to the values ​​detected by the process monitoring, for example if a too low oxidant content is detected, the oxidant addition can be increased, the temperature can be increased and / or the extraction and addition of process gas can be reduced. The control of the addition of process gas is directed, on the one hand, to the amount of particles carried in the process gas and / or, on the other hand, to the amount of process gas carrying the particles, which affects the concentration of the oxidant when it is added. In this way, process monitoring and control form a control loop.

[0030] A filter according to the invention for use in a method or device according to the invention is provided with a heating device configured as a resistive heater, in particular a wire mesh and / or a heating wire. The heating device can be configured as a resistive heater, which allows for a simple implementation. In particular, a wire mesh is suitable, which can be configured, for example, as a grid, net or irregular structure. The irregular structure can have different temperature ranges, for example depending on the local structure density. The wire mesh or heating wire can be inserted into the filter fabric. Since the filter is equipped with a heating device, the conversion of a conventional filter chamber into a post-treatment device and the application of the method for post-treatment are again simplified. Alternatively or additionally, the filter may be provided to provide an oxidizing agent or agent or further agent to initiate the oxidation reaction. For example, in terms of providing an oxidizing agent, the filter may be formed from or include a material that acts as an electron acceptor. In addition to the heating device, the filter may also act as a catalyst to initiate the oxidation reaction or to assist in the formation of an activated surface. Initiating the oxidation reaction at or in the region of the filter is also preferred in that it is there that the greatest particle accumulation is expected, where the oxidation reaction may be initiated periodically or when a critical mass is reached before the filter chamber is opened, particularly as part of process monitoring or closed loop control based on determined boundary conditions.

[0031] Further features and advantages of the present invention will become apparent from the following detailed description of the embodiments with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0032] [Figure 1] 1 is a schematic diagram showing, in partial cross section, an apparatus for producing a three-dimensional object; [Diagram 2] FIG. 2 is a schematic diagram showing, in partial cross section, a post-processing device according to a first embodiment of the present invention for post-processing particles transported in a process gas in a three-dimensional object production apparatus shown in FIG. 1, in which, in the embodiment, an oxidant supply section and a device for initiating an oxidation reaction are connected to a filter chamber. [Diagram 3] FIG. 2 is a schematic diagram showing, in partial cross section, a post-processing device according to a second embodiment of the present invention for post-processing particles transported in a process gas in the three-dimensional object production apparatus shown in FIG. 1, in which, in the embodiment, an oxidant supply section and a device for initiating an oxidation reaction are connected to a process gas supply section. [Figure 4] FIG. 2 is a schematic diagram, partially in cross section, of a third embodiment of a post-treatment device of the present invention for post-treatment of particles transported in a process gas in a three-dimensional object production apparatus as shown in FIG. 1, in which, in an embodiment, a supply of oxidant is directed to a filter, and the filter includes a device for initiating an oxidation reaction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] An apparatus for generating and manufacturing three-dimensional objects will now be described with reference to Fig. 1. The apparatus shown in Fig. 1 is a laser sintering or laser melting apparatus 1. For building up an object 2, the apparatus comprises a process chamber 3 having a chamber wall 4.

[0034] A vessel 5 having a vessel wall 6 and an open top is arranged in the treatment chamber 3. A working surface 7 is defined by the top opening of the vessel 5, and the area of ​​the working surface 7 located within the opening and used for building the object 2 is referred to as the building area 8. The treatment chamber 3 also comprises a treatment gas supply 31 connected to the treatment chamber 3, and an outlet 53 for the treatment gas.

[0035] In the container 5, a support 10 movable in the vertical direction V is arranged, on which a substrate 11 is arranged, which closes the container on its underside and forms its bottom. The substrate 11 may be a plate formed separately from the support 10, a plate fixed to the support 10 or may be formed integrally with the support 10. Depending on the powder used and the process used, a building platform 12 on which the object 2 is built may be attached to the substrate 11 as a building base. The object may also be built on the substrate 11 itself, in which case the substrate 11 serves as the building base. In FIG. 1, the object to be built on the building platform 12 in the container 5 is shown in an intermediate state with several solidified layers surrounded by a building material 13 that remains unsolidified below the working surface 7.

[0036] The apparatus 1 further comprises a reservoir 14 for a powdered build material 15 that can be solidified by electromagnetic radiation, and a recoater 16 that is movable in a horizontal direction H and applies a layer of the build material 15 into the build area 8. The recoater 16 preferably extends across the entire area to be applied, transverse to its direction of movement.

[0037] Optionally, a radiant heater 17 may be arranged in the process chamber 3 for heating the applied build material 15. As radiant heater 17, for example, an infrared emitter may be provided.

[0038] The laser sintering apparatus 1 further comprises an irradiation device 20 with a laser 21 which generates a laser beam 22 which is deflected by a deflection device 23 and focused by a focusing device 24 onto the working surface 7 through a coupling window 25 arranged at the top of the treatment chamber 3 in the chamber wall 4.

[0039] Furthermore, the laser sintering apparatus 1 comprises a control unit 29, by means of which the individual construction parts of the apparatus 1 are coordinately controlled in order to carry out the manufacturing process. Alternatively, the control unit 29 may be arranged partly or completely outside the apparatus 1. The control unit 29 may comprise a CPU, the operation of which is controlled by a computer program (software). The computer program may be stored in a storage medium separate from the apparatus 1 and loaded from this storage medium, in particular into the control unit.

[0040] Preferably, a powder material is used as the building material 15, the invention being directed in particular to building materials which form metal condensates, in the sense of an oxidation reaction, this includes building materials containing iron and / or titanium, and also materials containing copper, magnesium, aluminum, tungsten, cobalt, chromium and / or nickel, as well as compounds containing such elements.

[0041] In operation, the support 10 is lowered by a height corresponding to the desired thickness of the layer of the building material 15 in order to apply the powder layer. First, the recoater 16 moves to the storage container 14, from which it receives a sufficient amount of the building material 15 for applying the layer. The recoater 16 then moves over the building area 8, on which it applies and spreads the powdered building material 15 onto the building base or onto an already existing powder layer. The application is carried out over at least the entire cross section of the object 2 to be produced, and preferably over the entire building area 8, i.e. the area defined by the container wall 6. Optionally, the powdered building material 15 is heated to the working temperature by a radiant heater 17.

[0042] The laser light 22 is then scanned over the cross-section of the object 2 to be produced, solidifying the powdered build material 15 at locations corresponding to the cross-section of the object 2 to be produced. Here, the powder particles are partially or completely melted at these locations by the energy introduced by radiation, and after cooling, the powder particles are bonded together as a solid. These steps are repeated until the object 2 is finished and removed from the treatment chamber 3.

[0043] FIG. 2 is a schematic partial cross-sectional view of a post-treatment device 100 according to a first embodiment of the present invention for post-treatment of particles 51 entrained in a process gas 50 of the three-dimensional object generating and manufacturing apparatus 1 shown in FIG. 1. The particles 51 and the process gas 50 carrying the particles are respectively represented by arrows. The process gas 50 carrying the particles 51 enters the supply 52 of the process gas 50 from the process chamber 3 through an outlet 53, for example by suction, and flows into the filter chamber 40. In addition to the inlet for the supply 52 of the process gas 50 and the particles 51 contained therein, the filter chamber 40 includes an inlet for an oxidizing agent 60 supplied via an oxidizing agent supply 62, the oxidizing agent 60 also indicated by an arrow. The oxidizing agent supply 62 is directed towards the process gas 50 carrying the particles 51 leaving the supply 52, so that the oxidizing agent 60 can penetrate into the particle environment of the particles 51 in the starting region of the oxidation reaction described below. As a device for initiating the oxidation reaction, an energy input source 70, here configured as a radiant heater, is provided, which couples its thermal radiation to the filter chamber 40 through its transparent portion 42, which is significantly absorbed by the particles 51 entrained in the process gas 50, and which selectively heats the particles 51. The supply of oxidizer 60 to the particle environment of the particles 51, in combination with the particle temperature generated by the energy input source 70, results in an oxidation reaction in which the particles 51 burn off and / or are passivated in a controlled oxidation reaction, at least to such an extent that their tendency to burn and explode is sufficiently suppressed. The process gas 50 carrying the particles 51 or the particle residue is then removed through the filter 41, where the particles 51 or the particle residue remain, depending on the filter characteristics. The post-treatment device may further include a separator (not shown) to ensure that particles 51 formed from unsolidified build material 13 are separated from the treatment gas 50 and are not fed to the post-treatment device.

[0044] In the embodiment of Fig. 2, the oxidant supply 62, the supply 52 of the processing gas 50 and the energy input source 70 are arranged such that an oxidation reaction is initiated by the energy input source 70 in the particle environment, the oxidant 60 contacting the processing gas 50 carrying the particles 51 and thereby mixing with the particle environment. Alternatively, the particles 51 entrained in the processing gas 50 may first be heated to a temperature leading to the initiation of the oxidation reaction upon contact of the particles 51 with the oxidant 60. Similarly, the energy input for initiating the oxidation reaction may be performed after mixing of the particle environment with the oxidant 60 has already taken place, provided that the oxidant content is still sufficient at that time. This relates to both spatial and temporal aspects.

[0045] The post-treatment device of FIG. 2 also includes a control unit 80, which controls the oxidizer supply unit 62 to control the amount of oxidizer 60 supplied to the filter chamber, for example by a valve, controls the outlet 53 to control the amount of process gas 50 and particles 51 entrained therein, and controls the energy input source 70. To control at least one of these devices, which can be controlled by the control unit 80, a process monitor unit 90 is provided, which monitors at least the oxidizer content and the amount or temperature of particles in the filter chamber 40, particularly in a spatially resolved manner, via one or more sensors, such as sensors 91, 92 described with reference to FIG. 3. Here, these sensors may be included in the process monitor unit 90. The closed-loop control is performed by the control unit 80, but may also be constituted by a member separate from the control unit 80. The control unit 80 may be included in the control unit 29 of the laser sintering device 1 or may be assigned to the post-treatment device 100.

[0046] In contrast to the first embodiment shown in Fig. 2, in the post-treatment device 200 according to the second embodiment shown in Fig. 3, an oxidizing agent supply 621 and an energy input source in the form of a radiant heater 71 are linked to a supply 521 of a process gas 50 and entrained particles 51. 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 oxidizing agent supply 621 supplies an oxidizing agent 60 to the process gas 50 carrying the particles 51 in the supply section 5211 facing the process chamber 3. Alternatively, the supply may be provided in the intermediate section 5213, in particular upstream of the radiant heater 71 operating 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 supply section 5211 facing the treatment chamber 3 and the supply section 5212 facing the filter chamber 40. The intermediate section 5213 may therefore be a retrofit kit allowing easy adaptation of conventional equipment to a post-treatment device for the post-treatment of particles carried in the treatment gas 50. Here, the intermediate section 5213 has a circumferential radiation transparent section 524, through which energy is coupled to the intermediate section 5213 from an energy input source 71 also circumferentially around the longitudinal axis of the intermediate section 5213.

[0047] In the post-treatment device 200 according to Fig. 3, first, the oxidizing agent 60 is supplied to the processing gas 50 carrying the particles 51 in the supply section 5211 facing the processing chamber 3 through the oxidizing agent supply section 621, and the oxidizing agent 60 penetrates into the particle environment of the particles 51 carried in the processing gas 50. A mixture of the processing gas 50 carrying the particles 51 and the oxidizing agent 60 passes through the intermediate section 5213, where an oxidation reaction is initiated via the energy input source 71. For process monitoring by the control section 80 and closed-loop control based thereon, a sensor 91 is provided for detecting the amount of the particles 51 entrained in the processing gas 50 in the supply section 5211 facing the processing chamber 3, and a sensor unit 92 is provided for measuring the temperature and the oxidizing agent content in the intermediate section 5213.

[0048] In a fourth embodiment of the post-treatment device 300 shown in FIG. 4, an oxidizer supply 622 is connected to the filter chamber 40. That is, the oxidizer supply 622 is substantially directed to the filter 41 so that the oxidizer 60 flows around the filter 41 or is connected so that the oxidizer 60 permeates the filter 41. This allows the oxidizer 60 to be efficiently supplied to the particles 51 entrained in the process gas 50 at the filter 41. It is assumed that a large amount of particles 51 brought to the targeted oxidation reaction accumulates in the filter, especially in the case of a targeted oxidation reaction provided discontinuously. In a further aspect, the filter 41 can further comprise a resistive heater in the form of a heating wire 72 integrated into or surrounding the filter fabric, which serves as an energy input source for initiating the oxidation reaction. As already explained, the temperature input by the heating wire may additionally be used to support an oxidation reaction initiated by other means. Furthermore, a process monitoring system 90 is provided, which can provide the control unit 80 with information regarding, for example, the oxidizer content, the temperature, and / or the amount of particles 51 entrained in the process gas 50.

[0049] In one embodiment, the process monitoring system 90 detects the amount of particles 51 led to the filter chamber 40 and / or the filter 41 and, when a predetermined amount of particles 51 is reached, initiates the oxidation reaction with the addition of oxidizer 60 by the heating wire 72. Preferably, the oxidation reaction is performed such that the particles 51 burn off in the filter 41. Alternatively, in addition to the amount of particles 51, a predetermined time can be used as a criterion for initiating the oxidation reaction. As a further alternative, a further triggering event can be provided, for example by an operator's instruction before opening the filter chamber 40 and removing the filter 41. On the one hand, the various alternatives can be shifted to other embodiments, and on the other hand, the various alternatives can be combined with each other. The addition of oxidizer 60 via the oxidizer supply 622 can be controlled such that oxidizer 60 is made available to the filter chamber 40 when the oxidation reaction is or should be initiated. Alternatively, at least a minimum level of oxidizer content can in principle be continuously supplied to the filter chamber 40 or supplied such that a minimum level is maintained in the filter chamber 40. In a first variant, an oxidation reaction with the oxidizing agent 60 is avoided, unless the initiation of an oxidation reaction is intended. In a second variant, for example, a passivation of the particles 51 may be supported, so that the burn-off resulting from the initiation of an oxidation reaction is directed to those particles 51 whose tendency to burn and explode has not been sufficiently suppressed by the passivation. Here, a combination of a relatively low and constant oxidizing agent content in the filter chamber 40 or on the filter 41 and a variant in the sense of an increase in the oxidizing agent content at a given time may be provided, for example when a given amount of particles 51 is reached, after a given time has elapsed or on demand.

Claims

1. A method for the post-treatment of particles (51) carried by a process gas (50) in an apparatus (1) for the production and manufacture of three-dimensional objects, comprising the steps of: The particles (51) are introduced into a filter chamber (40), The process gas (50) is formed by the gas discharged from the process chamber (3) of the device (1) for the production of the product, An oxidizing agent (60) is added to the particles (51) to initiate an oxidation reaction between the oxidizing agent (60) and the particles (51); the added oxidant (60) is provided to and / or is present in a particulate environment formed by the process gas; The method of post-treatment, characterized in that the particles (51) are heated.

2. 2. The method of claim 1, wherein the process gas is recycled and / or formed by and / or includes an inert gas.

3. 3. The method of claim 1 or 2, wherein the oxidizing agent (60) is provided in a flowable material state.

4. 4. The method of claim 3, wherein the oxidant (60) is provided in a gaseous state of matter.

5. 5. The method of claim 4, wherein the oxidant (60) is provided in the form of oxygen.

6. The method according to any one of claims 1 to 5, characterized in that the oxidizing agent (60) added to the particles (51) has a volume fraction of 0.01 volume % or more and 20 volume % or less with respect to the particle environment.

7. 7. The method according to claim 6, characterized in that the oxidizing agent (60) added to the particles (51) has a volume fraction of 1% to 10% by volume relative to the particle environment.

8. 8. The method according to claim 7, characterized in that the oxidizing agent (60) added to the particles (51) has a volume fraction of 4% to 6% by volume relative to the particle environment.

9. The method according to any one of the preceding claims, characterized in that the particles (51) are heated to a temperature between 50°C and 650°C.

10. 10. The method of claim 9, wherein the particles (51) are heated to a temperature between 75°C and 200°C.

11. 11. The method of claim 10, wherein the particles (51) are heated to a temperature between 100°C and 150°C.

12. 12. The method according to any one of claims 1 to 11, characterized in that the oxidant content surrounding the particle (51) and / or the temperature of the particle environment and / or the temperature of the particle (51) itself are detected and used to control an oxidant supply (62, 621, 622) and / or a heating device (70, 71, 72) and / or an outlet (53).

13. A post-treatment device (100, 200, 300) for post-treatment of particles (51) carried by a treatment gas (50) in an apparatus (1) for the production and manufacture of a three-dimensional object, the particles (51) being guided to a filter chamber (40), The process gas (50) is formed by the gas discharged from the process chamber (3) of the device (1) for the production of the product, The post-treatment device (100, 200, 300) includes an oxidizing agent supplying section (62, 621, 622) for adding an oxidizing agent (60) to the particles (51) and a device for initiating an oxidation reaction between the oxidizing agent (60) and the particles (51), the oxidant supply (62, 621, 622) is configured to supply the oxidant (60) to a particulate environment formed by the process gas (50); The post-treatment device is characterized in that the particles (51) are heated.

14. 14. The aftertreatment device according to claim 13, characterized in that the oxidant supply (62, 621, 622) is linked to the process gas supply (52, 521) and / or is connected to the filter chamber (40).

15. 15. An aftertreatment device according to claim 13 or 14, characterized in that the oxidant supply is directed to at least one filter (41) in the filter chamber (40).

16. 15. The post-treatment device according to claim 13, further comprising a control unit (80) for controlling the oxidant supply unit to supply the oxidant continuously, periodically, or variably.

17. 17. The aftertreatment device of claim 16, wherein the control unit (80) is a closed loop control unit.

18. 18. An aftertreatment device according to claim 16 or 17, characterized in that it comprises at least one energy input source (70, 71, 72).

19. 19. The aftertreatment device according to claim 18, characterized in that the energy input of the energy input sources (70, 71, 72) is provided from outside the filter chamber (40) and / or from inside the filter chamber (40).

20. 20. The aftertreatment device according to claim 19, characterized in that the energy input is provided via a radiation transparent portion (42) in the filter chamber (40) and / or via an energy input element integrated in at least one filter (41) in the filter chamber (40).

21. The post-treatment device according to any one of claims 18 to 20, characterized in that at least one of the energy input sources (70, 71, 72) is configured as a heating device and / or an energy source controlled and / or regulated by the control unit (80).

22. The post-treatment device according to any one of claims 18 to 21, further comprising a process monitoring unit (90) for monitoring an oxidant content, a particle amount, and / or a temperature.

23. 23. The aftertreatment device of claim 22, wherein during operation, the control unit (80) controls the oxidant supply unit (62, 621, 622) and / or the energy input source (70, 71, 72) and / or the exhaust (53) based on the process monitor unit (90).

24. A filter (41) for use in a method according to any one of claims 1 to 12 and / or in a device (100, 200, 300) according to any one of claims 13 to 23, comprising: The filter (41) is characterized in that it comprises a heating device (72) configured as a resistive heater.

25. 25. The filter of claim 24, wherein the resistive heater is configured as a wire mesh and / or a heating wire.

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