METHOD AND DEVICE FOR POST-TREATMENT OF PARTICLES CARRIED IN A PROCESS GAS AND FILTER THEREFOR

Abstract

The present invention relates to a method for the post-treatment of particles (51) carried along in a process gas (50) of a device (1) for the generative manufacturing of three-dimensional objects, wherein the particles (51) are conducted to a filter chamber (40). An oxidant (60) is added to the particles (50) and that an oxidation reaction of the particles (50) with the oxidant (60) is initiated.

Claims

1. Method for a post-treatment of particles carried along in a process gas of a device for the generative manufacturing of three-dimensional objects, wherein the particles are conducted to a filter chamber, and wherein an oxidant is added to the particles and an oxidation reaction of the particles with the oxidant is initiated.

2. Method according to claim 1, wherein the added oxidant is supplied to a particle environment and/or is present in a particle environment, which is provided in the form of inert gas.

3. Method according to claim 1, wherein the oxidant is provided in the form of oxygen.

4. Method according to claim 3, wherein a volume fraction of oxygen, of at least 0.01 vol. % and at most 20 vol. %, relative to the particle environment, is added to the particles.

5. Method according to claim 1, wherein the particles are heated to a temperature of at least 50° C. and at most 650° C.

6. Method according to claim 1, wherein an oxygen content surrounding the particles, and/or the temperature of the particle environment and/or of the particles themselves is or are detected and influence(s) the control of an oxidant supply and/or of a heating device and/or of an outlet.

7. Post-treatment device for post-treatment of particles carried along in a process gas of a device for the generative manufacturing of three-dimensional objects, wherein the particles are conducted to a filter chamber, and wherein the post-treatment device comprises an oxidant supply for the addition of oxidant to the particles and a device for initiating an oxidation reaction of the particles with the oxidant.

8. Post-treatment device according to claim 7, wherein the oxidant supply is associated with the supply of the process gas and/or connected to the filter chamber.

9. Post-treatment device according to claim 7, wherein the oxidant supply is essentially directed towards at least one filter in the filter chamber.

10. Post-treatment device according to claim 7, wherein a closed-loop control is provided that controls the oxidant supply in such a way that it supplies the oxidant continuously, periodically, or variably.

11. Post-treatment device according to claim 7, wherein the post-treatment device comprises at least one energy input source whose energy input is effected from outside the filter chamber through a radiation-transparent portion, in an interior of the filter chamber and/or from inside the filter chamber through an energy input element integrated in the at least one filter.

12. Post-treatment device according to claim 11, wherein the at least one energy input source is configured as a heating device.

13. Post-treatment device according to claim 7, wherein a process monitoring is provided that monitors an oxygen content, the particle amount, and/or the temperature.

14. Post-treatment device according to claim 13, wherein, during operation, the control controls the oxidant supply and/or an energy input source and/or an outlet on the basis of the process monitoring.

15. Filter for use in a method according to claim 1 and/or in a device according to claim 7, wherein the filter comprises a heating device, which is configured as a resistance heater, in particular a wire mesh and/or a heating wire.

16. Method according to claim 1, wherein the oxidant is added to the particles by an oxidant supply being associated with a supply of the process gas and/or being connected to the filter chamber.

17. Method according to claim 1, wherein the oxidant is added to the particles such that the oxidation reaction takes place before the particles reach the filter chamber and/or such that the oxidation reaction is limited to the region of the filter chamber.

18. Method according to claim 1, wherein the oxidation is initiated by an energy input and/or a catalyst and/or adding activating agents and/or electrolysis.

19. Method according to claim 1, wherein the process gas is a gas being discharged from a process chamber of the device for the generative manufacturing, and wherein the added oxidant is supplied to a particle environment and/or is present in a particle environment which is formed by the process gas.

20. Method according to claim 19, wherein the particles are heated, wherein the process gas is recirculated, and wherein the process gas is an inert gas or comprises an inert gas.

21. Post-treatment device according to claim 7, wherein the process gas is a gas being discharged from a process chamber of the device for the generative manufacturing, and wherein the oxidant supply is configured to add the oxidant to a particle environment which is formed by the process gas.

Description

[0057] Further features and expediencies of the invention follow from the description of embodiments with reference to the appended drawings.

[0058] FIG. 1 is a schematic view, partially shown as sectional view, of a device for the generative manufacturing of a three-dimensional object.

[0059] FIG. 2 is a schematic view, partially shown as sectional view, of a post-treatment device for a post-treatment of particles carried along in a process gas of a device for the generative manufacturing of a three-dimensional object in connection with a device according to FIG. 1 according to a first embodiment of the invention, in which in an embodiment the supply of the oxidant and the device for initiating the oxidation reaction may be associated with the filter chamber.

[0060] FIG. 3 is a schematic view, partially shown as sectional view, of a post-treatment device for a post-treatment of particles carried along in a process gas of a device for the generative manufacturing of a three-dimensional object in connection with a device according to FIG. 1 according to a second embodiment of the invention, in which in an embodiment the supply of the oxidant and the device for initiating the oxidation reaction may be associated with the supply of the process gas.

[0061] FIG. 4 is a schematic view, partially shown as sectional view, of a post-treatment device for the post-treatment of particles carried along in a process gas of a device for the generative manufacturing of a three-dimensional object in connection with a device according to FIG. 1 according to a third embodiment of the invention, in which in an embodiment the supply of the oxidant is directed to the filter and the filter comprises the device for initiating the oxidation reaction.

[0062] In the following, a device for the generative manufacturing of a three-dimensional object is described with reference to FIG. 1. The device shown in FIG. 1 is a laser sintering or laser melting device 1. To construct an object 2, it contains a process chamber 3 with a chamber wall 4.

[0063] In the process chamber 3, a container 5 being open at the top having a container wall 6 is arranged. A working plane 7 is defined by the upper opening of the container 5, wherein the area of the working plane 7 that lies within the opening and which may be used for the construction of the object 2 is referred to as build area 8. In addition, the process chamber 3 comprises a process gas supply 31 associated with the process chamber 3 and an outlet 53 for the process gas.

[0064] In the container 5, a support 10, which can be moved in a vertical direction V, is arranged, at which a base plate 11, which closes the container towards its underside and therefore forms its bottom, is arranged. The base plate 11 may be a plate which is formed separately from the support 10 and which is fastened to the support 10 or it 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 base plate 11 as building base. The object may also be built on the base plate 11 itself, which then serves as building base. In FIG. 1, the object to be formed on the building platform 12 in the container 5 is shown underneath the working plane 7 in an intermediate state having a plurality of solidified layers surrounded by building material 13 remaining unsolidified.

[0065] The device 1 further contains a storage container 14 for pulverulent building material 15, which can be solidified by electromagnetic radiation, and a recoater 16, which is movable in a horizontal direction H, for applying layers of the building material 15 within the build area 8. Preferably, the recoater 16 extends over the entire area to be coated transversely to its direction of movement.

[0066] Optionally, a radiation heater 17, which serves to heat the applied building material 15, is arranged in the process chamber 3. As radiation heater 17, for instance an infrared emitter, may be provided.

[0067] The laser sintering device 1 further comprises an irradiation device 20 with a laser 21, which generates a laser beam 22, which is deflected by a deflecting device 23 and focused onto the working plane 7 by a focusing device 24 via a coupling window 25, which is arranged at the top of the process chamber 3 in the chamber wall 4.

[0068] Further, the laser sintering device 1 comprises a control unit 29 by way of which the individual component parts of the device 1 are controlled in a coordinated manner for executing the manufacturing process. Alternatively, the control unit 29 may be arranged partially or completely outside the device 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 on a storage medium being separate from the device 1, from which it may be loaded into the device 1, in particular in the control unit.

[0069] Preferably, a pulverulent material is used as the building material 15, wherein the invention is in particular directed to building materials forming metal condensates. In the sense of an oxidation reaction, this includes in particular building materials containing iron and/or titanium, but also materials containing copper, magnesium, aluminium, tungsten, cobalt, chromium and/or nickel, as well as compounds containing such elements.

[0070] During operation, the support 10 is lowered by a height which corresponds to the desired thickness of the layer of the building material 15 in order to apply a powder layer. First, the recoater 16 moves to the storage container 14 and receives therefrom an amount of building material 15 which is sufficient for applying a layer. Then, it moves over the build area 8, applies thereon pulverulent building material 15 on the building base or an already previously present powder layer and spreads it into a powder layer. The application is done over at least the entire cross-section of the object 2 to be manufactured, preferably over the entire build area 8, i.e. the area defined by the container wall 6. Optionally, the building material 15 in powder form is heated to a working temperature by means of the radiation heater 17.

[0071] Subsequently, the cross-section of the object 2 to be manufactured is scanned by the laser beam 22 such that the pulverulent building material 15 is solidified at those positions that correspond to the cross-section of the object 2 to be manufactured. Herein, the powder particles are partially or completely melted at these positions by the energy introduced by the radiation such that, after cooling, they are bonded together as a solid. These steps are repeated until the object 2 is completed and may be taken out of the process chamber 3.

[0072] FIG. 2 is a schematic, partially sectional view of a post-treatment device 100 for post-treatment of particles 51 entrained in a process gas 50 of a device for the generative manufacturing of three-dimensional objects in connection 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 along are represented by the respective arrow. The process gas 50 carrying the particles 51 is let out of the process chamber 3 through an outlet 53 into the supply 52 of the process gas 50 to the filter chamber 40, for example by suction. In addition to an inlet for the feed 52 of the process gas 50 and the particles 51 contained therein, the filter chamber 40 comprises an inlet for an oxidant 60 supplied via an oxidant supply 62, also shown as an respective arrow. The oxidant feed 62 is oriented towards the process gas 50 carrying particles 51 that exits from the supply 52 in such a way that the oxidising agent 60 can penetrate the particle environment of the particles 51 in the region of the initiation of the oxidation reaction described below. As device for initiating the oxidation reaction, an energy input source 70 configured as a radiant heater is provided here, which couples its thermal radiation into the filter chamber 40 via a transparent portion 42 of the same, and it is significantly absorbed by the particles 51 entrained in the process gas 50, so that the latter are selectively heated. The supply of the oxidant 60 into the particle environment of the particles 51, in combination with the particle temperature generated by the energy input source 70, leads to an oxidation reaction in which the particles 51 burn off and/or are passivated at least in a controlled oxidation reaction to such an extent that their tendency to burn and explode is sufficiently inhibited. The process gas 50 carrying the particles 51, or now particle residues, is then drawn off through the filter 41, where the particles 51 or particle residues remain according to the filter characteristics.

[0073] The post-treatment device may further comprise a separator, which is not shown, so that particles 51 formed from unsolidified building material 13 are separated from the process gas 50 so that they are not fed to the post-treatment device.

[0074] In the embodiment according to FIG. 2, the oxidant supply 62, the supply 52 of the process gas 50 and the energy input source 70 are arranged in such a way that the oxidation reaction is initiated by the energy input source 70 in the particle environment in which the oxidant 60 meets the process gas 50 carrying the particles 51 and thereby mixes with the particle environment. Alternatively, the particles 51 entrained in the process gas 50 may first be heated to a temperature which then leads to initiation of an oxidation reaction upon contact of the particles 51 with the oxidant 60. Equally, the energy input to initiate the oxidation reaction may also take place after the mixing of the particle environment with the oxidant 60 has already taken place, provided that the oxidant content is then still sufficient. This refers to both a spatial and a temporal aspect.

[0075] In addition, the post-treatment device in FIG. 2 comprises a control 80 which can control the oxidant supply 62 and thus the amount of oxidant 60 supplied to the filter chamber, for example by valves, the outlet 53 and thus the amount of process gas 50 and particles 51 entrained therein, as well as the energy input source 70. For the control of at least one of these devices, which may be controlled by the control 80, a process monitoring 90 is provided, which monitors at least the oxidant content, the amount of particles or the temperature in the filter chamber 40, in particular spatially resolved, via one or more sensors, such as the sensors 91 and 92, which are described by way of example for FIG. 3, and which may be included here in the process monitoring 90. The closed-loop control is carried out by the control 80, but may also be formed by a unit separate from the latter. The control 80 may also be included in the control unit 29 of the laser sintering device 1 or be allocated to the post-treatment device 100.

[0076] In contrast to the first embodiment shown in FIG. 2, in the post-treatment device 200 according to a second embodiment shown in FIG. 3, the oxidant supply 621 and the energy input source in the form of a radiation heater 71 are associated with the supply 521 of the process gas 50 and the particles 51 entrained 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 oxidant supply 621 supplies the oxidant 60 to the process gas 50 carrying the particles 51 in the supply section 5211 facing the process chamber 3. Alternatively, the supply may also be provided in the intermediate section 5213, in particular upstream of the radiation 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 in such a way that it can be inserted between the supply section 5211 facing the process chamber 3 and the supply section 5212 facing the filter chamber 40. Accordingly, the intermediate section 5213 may be a retrofit kit that easily allows for adaptation of conventional equipment into a post-treatment device for the post-treatment of particles carried in a process gas 50. Here, the intermediate section 5213 has a circumferential radiation-transparent portion 524 through which energy from an energy input source 71 also circumferential about a longitudinal axis of the intermediate section 5213 is coupled into the intermediate section 5213.

[0077] In the post-treatment device 200 according to FIG. 3, the oxidant 60 is first supplied to the process gas 50 carrying the particles 51 in the supply section 5211 facing the process chamber 3 via the oxidant supply 621 such that the particle environment of the particles 51 carried in the process gas 50 is permeated with the oxidant 60. The mixture of the process gas 50 carrying the particles 51 and the oxidant 60 passes through the intermediate section 5213, in which the oxidation reaction is initiated via the energy input source 71. For process monitoring and closed-loop control based thereon by the control 80, a sensor 91 is provided for detecting the amount of particles 51 entrained in the process gas 50 in the supply section 5211 facing the process chamber 3, and a sensor unit 92 is provided for measuring the temperature and the oxidant content in the intermediate section 5213.

[0078] In the fourth embodiment of the post-treatment device 300 shown in FIG. 4, the oxidant supply 622 is connected to the filter chamber 40 in such a way that the oxidant supply 622 is directed substantially towards the filter 41 and thus the oxidant 60 flows around the filter 41 or the filter 41 is penetrated by the oxidant 60. This allows the oxidant 60 to be efficiently supplied to the particles 51 entrained in the process gas 50 at the filter 41. Particularly in the case of a non-continuously provided targeted oxidation reaction, the largest accumulation of particles 51 to be brought to the targeted oxidation reaction is to be assumed at the filter. In a further development, the filter 41 may further comprise 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 temperature input by the heating wire may also be additionally used to support an oxidation reaction initiated by other means. In addition, a process monitoring system 90 is provided which may, for example, provide information to the control 80 regarding the oxidant content, the temperature and/or the amount of particles 51 entrained in the process gas 50.

[0079] In one embodiment, the process monitoring 90 detects the amount of particles 51 conducted to the filter chamber 40 and/or the filter 41 in order to initiate the oxidation reaction with the addition of the oxidant 60 by the heating wire 72 when a predetermined amount of particles 51 is reached. Preferably, an oxidation reaction is effected such that the particles 51 burn off at the filter 41. Alternatively, in addition to the amount of particles 51, a predetermined period of time may be used as a criterion for initiating an oxidation reaction. In a further alternative, a further triggering event may also be provided, for example by instruction of the operator before the filter chamber 40 is opened to remove the filter 41. On the one hand, the various alternatives may be transferred to the other embodiments, but on the other hand, they may also be combined with each other. The addition of the oxidant 60 via the oxidant supply 622 may be controlled in such a way that the oxidant 60 is made available to the filter chamber 40 when the oxidation reaction is initiated or is to be initiated. Alternatively, at least a minimum level of oxidant content may in principle be continuously supplied to the filter chamber 40 or supplied such that the minimum level is maintained in the filter chamber 40. In the first variant, an oxidation reaction with the oxidant 60 is avoided as long as no initiation of the oxidation reaction is provided. In the second variant, for example passivation of the particles 51 may be supported such that the burn-off resulting from the initiation of the oxidation reaction is directed at the particles 51 that have not been sufficiently inhibited in their tendency to burn and explode by the passivation. Here, too, a combination of the variants may be provided in the sense of a comparatively low constant oxidant content in the filter chamber 40 or on the filter 41 and an increase in the oxidant content at predetermined times, i.e. for example when a predetermined amount of particles 51 is reached, after a predetermined period of time, or on demand.