METHOD FOR MODERATING A REACTION OF METAL PARTICLES

Abstract

Method for moderating a reaction of metal particles, in particular metal condensates, preferably from an additive manufacturing process, in particular a laser sintering or laser melting process, wherein the metal particles are combined, in particular mixed, with an at least partially meltable inerting material, wherein the inerting material comprises particles with a particle size of less than or equal to 100 .Math.m.

Claims

1. Method for moderating a reaction of metal particles from an additive manufacturing process, wherein the metal particles are combined with an at least partially meltable inerting material, wherein the inerting material comprises particles with a particle size of less than or equal to 100 .Math.m.

2. Method according to claim 1, wherein the inerting material comprises at least 10% by weight, of particles having a particle size of less than or equal to 100 .Math.m and/or greater than or equal to 0.1 .Math.m.

3. Method according to claim 1 , wherein the inerting material comprises glass and/or at least one salt.

4. Method according to claim 1, wherein the inerting material comprises less than 10% by weight of lime .

5. Method according to claim 1, wherein at least one meltable component of the inerting material has a melting temperature, at normal pressure of 1.0 bar, of at most 1200° C. .

6. Method according to claim 1, wherein at least one meltable component of the inerting material has a melting temperature, at normal pressure of 1.0 bar, of at least 100° C. .

7. A method comprising: moderating a reaction of metal particles from an additive manufacturing process with a meltable inerting material, wherein the inerting material comprises particles with a particle size of less than or equal to 100 .Math.m.

8. Additive manufacturing process comprising the method of moderating a reaction of metal particles according to claim 1.

9. Manufacturing apparatus– for additive manufacturing of objects comprising a meltable inerting material for moderating a reaction of metal particles according to the manufacturing process according to claim 8, wherein the inerting material comprises particles having a particle size smaller than or equal to 100 .Math.m.

10. Combination comprising metal particles from an additive manufacturing process according to claim 8, and an at least partially meltable inerting material, wherein the inerting material comprises particles having a particle size smaller than or equal to 100 .Math.m.

Description

[0049] In the following, the invention will be described with reference to examples of embodiments, which will be explained in more detail with reference to the figures.

[0050] Hereby show:

[0051] FIG. 1 a schematic illustration, partially reproduced as a cross-section, of a device for the layer-by-layer build-up of a 3-dimensional object;

[0052] FIG. 2 a schematic representation of a formation of metal particles;

[0053] FIG. 3 a diagram of a minimum ignition temperature in °C as well as a proportion of an inerting material in % by weight; and

[0054] FIG. 4 a diagram of a burning rate in cm/s as well as a proportion of inerting material in % by weight.

[0055] In the following description, the same reference numerals are used for the same and same-acting parts.

[0056] The device shown in FIG. 1 is a laser sintering or laser melting device a1 known per se. For building-up an object a2 it contains a process chamber a3 with a chamber wall a4. In the process chamber a3, an upwardly open build-up container a5 with a wall a6 is arranged. A working plane a7 is defined by the upper opening of the build-up container a5, wherein the area of the working plane a7 lying within the opening, which can be used to build the object a2, is referred to as the build-up area a8. In the container a5 a support a10, which is movable in a vertical direction V, is arranged, to which a base plate a11 is attached, which closes off the build-up container a5 at the bottom and thus forms its base. The base plate a11 can be a plate formed separately from the support a10 and attached to the support a10, or it can be formed integrally with the support a10. Depending on the powder and process used, on the base plate a11 there may also be attached a building platform a12 on which the object a2 is built. However, the object a2 can also be built on the base plate a11 itself, which then serves as the building platform. In FIG. 1, the object a2 to be formed in the build-up container a5 on the building platform a12 is shown below the working plane a7 in an intermediate state with several solidified layers surrounded by build-up material a13 that has remained unsolidified. The laser sintering device a1 further comprises a storage container a14 for a owedered build-up material a15 solidifiable by electromagnetic radiation and a coater a16 movable in a horizontal direction H for applying the build-up material a15 to the build-up area a8. The laser sintering device a1 further comprises an exposure device a20 having a laser a21 which generates a laser beam a22 as an energy beam bundle which is deflected via a deflection device a23 and focused onto the working plane a7 by a focusing device a24 via a coupling window a25 which is provided on the upper side of the process chamber a3 in the wall a4 thereof.

[0057] Further, the laser sintering device a1 includes a control unit a29 via which the individual components of the device a1 are controlled in a coordinated manner to perform the build-up process. The control unit a29 may include a CPU whose operation is controlled by a computer program (software). The computer program may 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. In operation, to apply a powder coating, the support a10 is first lowered by a height corresponding to the desired layer thickness.

[0058] By moving the coater a16 over the working plane a7, a layer of the pulverulent build-up material a15 is then applied. For safety, the coater a16 pushes a slightly larger amount of build-up material a15 in front of it than is required to build up the layer. The coater a16 pushes the scheduled excess of build-up material a15 into an overflow container a18.

[0059] On each side of the build-up container a5 an overflow container a18 is arranged. The application of the powdered build-up material a15 takes place at least over the entire cross section of the object a2 to be produced, preferably over the entire build-up area a8, i.e., the area of the working plane a7 that can be lowered by a vertical movement of the support a10. Subsequently, the cross-section of the object a2 to be manufactured is scanned by the laser beam a22 with a radiation impact area (not shown), which schematically represents an intersection of the energy beam with the working plane a7. As a result, the powdered build-up material a15 is solidified at locations corresponding to the cross-section of the object a2 to be manufactured. These steps are repeated until the object a2 is completed and can be removed from the build-up container a5.

[0060] For generating a preferably laminar process gas flow a34 in the process chamber a3, the laser sintering device a1 further comprises a gas supply channel a32, a gas inlet nozzle a30, a gas outlet opening a31 and a gas discharge channel a33. The process gas flow a34 moves horizontally across the build-up area a8. The gas supply and discharge may also be controlled by the control unit a29 (not shown). The gas exhausted from the process chamber a3 may be fed to a filtering device (not shown), and the filtered gas may be fed back to the process chamber a3 via the gas supply channel a32, forming a recirculation system with a closed gas loop. Instead of only one gas inlet nozzle a30 and one gas outlet opening a31, several nozzles or openings can be provided in each case.

[0061] In this case, condensed metal particles can now be present on and/or removed from, for example, the wall a4 or the (not shown) filter device. This material should then preferably be moderated according to the invention.

[0062] In FIG. 2 it is schematically illustrated how the metal particles are presumably created according to the embodiment. A laser beam 10 is hereby moved over a surface 11. A corresponding direction of movement is symbolised by the arrow 12. The laser beam 10 melts starting material 13, whereby a part of the starting material is vaporised. The molten starting material is marked with the reference sign 16, the gaseous starting material with the reference sign 17. A so-called vapour capillary is formed at the point where the laser beam impinges. This contains vaporised material (e.g. metal) at high temperatures as plasma. It is ejected from the vapour capillary (keyhole) at high speeds due to buoyancy effects and material flowing up from below or subsequently vaporised. By cooling of the metal vapour a supersaturation of the gas phase and thus a condensation (homogeneous condensation) is caused. From this condensation metal particles 14 are formed. This can still form agglomerates 15 in the further course of time.

[0063] In FIGS. 3 and 4 the effect of an inerting material (here: glass powder) on a minimum ignition temperature and a burning rate in the case of an iron condensate (starting point is the high-alloy forged steel MS1) is explained.

[0064] According to FIG. 3, the addition of glass powder can significantly raise a minimum ignition temperature at which spontaneous ignition takes place. In comparison, lime powder showed significantly lower minimum ignition temperatures at high proportions.

[0065] Particularly good results could be achieved with a comparatively fine grain size (particle size), especially so that the inerting material is comparatively cohesive.

[0066] According to FIG. 4, a burning rate could be progressively reduced by adding glass powder. Here, too, it was found that a comparatively fine particle size (grain size), so that the inerting material is cohesive and can be mixed well with the metal condensate, is advantageous.

[0067] At this point, it should be noted that all the parts described above, considered alone and in any combination, in particular the details shown in the drawings, are claimed to be essential to the invention. Modifications thereof are familiar to the skilled person.

LIST OF REFERENCE SIGNS

[0068] a1 laser sintering or laser melting device [0069] a2 object [0070] a3 process chamber [0071] a4 chamber wall [0072] a5 build-up container [0073] a6 wall [0074] a7 working plane [0075] a8 build-up area [0076] a10 movable support [0077] a11 base plate [0078] a12 building platform [0079] a13 unsolidified build-up material [0080] a14 storage container [0081] a15 powdered build-up material / aluminium alloy [0082] a16 movable coater [0083] a20 exposure device [0084] a21 laser [0085] a22 laser beam [0086] a23 deflection device [0087] a24 focusing device [0088] a25 coupling window [0089] a29 control unit [0090] a30 gas inlet nozzle [0091] a31 gas outlet opening [0092] a32 gas supply channel [0093] a33 gas discharge channel [0094] a34 laminar process gas flow [0095] H horizontal direction [0096] V vertical direction [0097] 10 laser beam [0098] 11 surface [0099] 12 arrow [0100] 13 starting material [0101] 14 metal particle [0102] 15 agglomerate (of metal particles) [0103] 16 molten starting material [0104] 17 vaporised starting material