METHOD FOR PRODUCING AN ADDITIVELY MANUFACTURED PRODUCT FROM A MINERAL STARTING MATERIAL BY MEANS OF DIRECT LASER SINTERING, AND LIGHTWEIGHT PART PRODUCED BY MEANS OF SAID METHOD

Abstract

The invention relates to a method for utilizing mineral materials for additive manufacturing that can be implemented more quickly, more economically and with greater technical simplicity, in comparison with common additive manufacturing, by virtue of controlled expansion in the sintering process by means of a laser source. The entire production process is free of organic materials and allows previously unfeasible end uses in the fields of acoustic insulation, thermal insulation, fire protection, filtration, design objects and lightweight components to be realized. In particular, the invention relates to a method for producing a product by means of 3-D printing or additive manufacturing, wherein an open-pore lightweight part is constructed layer-by-layer, without the use of organic binders or other organic auxiliary agents, from a pulverous mineral starting raw substance of natural origin, which raw substance is obtained without chemical alteration of the solid constituents of the natural material, and wherein, beginning with the second layer, the most recently applied layer is bonded to the surface of the existing body of the lightweight part by means of immediately subsequently performed direct selective laser sintering.

Claims

1. A method for producing a product by means of 3-D printing or additive manufacturing, characterized in that an open-pore lightweight part (13) is constructed layer by layer, without the use of organic binders or other organic auxiliary agents, from a powdered mineral raw starting material (1) of natural origin that is obtained without chemical alteration of the solid components of the natural material, and wherein, beginning with the second layer, in each case the most recently applied layer is bonded to the surface of the existing body of the lightweight part (27) by means of direct selective laser sintering that is performed immediately afterward.

2. The method according to claim 1, characterized in that apart from the laser radiation, it is not necessary either for the produced lightweight part (13) to undergo a subsequent sintering process or additional preheating.

3. The method according to claim 1, characterized in that a powdered mineral raw starting material (1) is used that has an SiO.sub.2 proportion between 50 and 85 wt %, preferably perlite having an SiO.sub.2 proportion of 70 to 75 wt %.

4. The method according to claim 1, characterized in that a laser having a wavelength of 5 μm or greater, preferably a CO.sub.2 laser (10), is used.

5. The method according to claim 1, characterized in that the energy of the laser is absorbed by the mineral raw starting material (1) and converted into heat, which in turn melts the individual grains of the raw starting material (1) onto the surface, thus thermally melting or sintering (25) the grains to one another.

6. The method according to claim 1, characterized in that the expansion or blowing (23) of the raw starting material (1) that is exposed to the laser radiation, caused by the thermal energy of the laser beam, counteracts shrinkage of the printed lightweight part (13) that would otherwise occur during a laser sintering process.

7. The method according to claim 1, characterized in that the raw starting material (1) has a moisture content between 0.1 and 5.0 wt %, preferably a moisture content between 0.5 and 2.0 wt %.

8. The method according to claim 1, characterized in that the raw starting material (1) has a bulk density between 100 and 700 kg/m.sup.3, preferably a bulk density of 300 to 500 kg/m.sup.3.

9. The method according to claim 1, characterized in that the mineral raw starting material (1) has a grain size between 1 and 500 μm, preferably a grain size greater than 80 μm, preferably as the result of dry sieving or at least a similar separation process.

10. The method according to claim 1, characterized in that the thickness of an individual layer is between 0.01 and 1.2 mm, preferably between 0.4 and 0.8 mm.

11. The method according to claim 1, characterized in that the mineral raw starting material (1) undergoes thermal pretreatment, in particular in the form of expansion or blowing.

12. The method according to claim 1, characterized in that for an optimally uniform application by means of a leveling roller, the mineral raw starting material (1) is uniformly recompacted over the entire surface for at least 20 seconds per 2 to 7 cm of the filled material, preferably per 5 cm of the filled material, for example by machine with the aid of a vibrating table at a vibration frequency of preferably 40 to 60 Hz, or manually with the aid of a hand stamper, preferably having a weight between 5 and 10 kg at a drop height of 1 to 3 cm.

13. The method according to claim 1, characterized in that the power of the laser is between 10 and 10,000 W.

14. The method according to claim 1, characterized in that the scanning speed of the laser beam (10) is between 20 and 10,000 mm/s.

15. The method according to claim 14, characterized in that the ratio of the laser power to the scanning speed is between 0.01 and 1 Ws/mm, preferably between 0.05 and 0.3 Ws/mm.

16. The method according to claim 1, characterized in that during the sintering of perlite or modified perlite, fumed silica results as a by-product, for example having an SiO.sub.2 proportion of 75 wt % to 99 wt %, preferably having an SiO.sub.2 proportion of 80 wt % to 90 wt %, in particular having an SiO.sub.2 proportion of approximately 85 wt %.

17. The method according to claim 1, characterized in that the by-product that results during the sintering of perlite or modified perlite, preferably the fumed silica, is electrostatically separated from the exhaust air in the area of the printing device.

18. An open-pore lightweight part (13) that is made of a powdered mineral raw starting material (1) and produced using a method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further features, advantages, properties, and effects based on the invention result from the following description of one exemplary embodiment of the invention, with reference to the drawings. In the drawings:

[0041] FIG. 1 shows a schematic view of a device that is suitable for carrying out the method according to the invention, and

[0042] FIG. 2 shows an enlarged detail of the direct laser sintering of the powder from FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] A device that is suitable for carrying out the method according to the invention includes a powder storage chamber 1 with a first piston 2, and a construction chamber 5 with a second piston 3 (see FIG. 1).

[0044] At the start of the printing operation the mineral material, which is present in powdered form, is poured into the powder storage chamber 1. When an exchangeable, mobile powder storage chamber 1 is used, it is filled with powder delivered on a conveyor belt from an upstream silo.

[0045] The filled powder is then compacted for 30 seconds on a vibrating table at a vibration frequency of 50 Hz, and the excess material is then scraped off using a straightedge.

[0046] For a fixed powder storage chamber 1 in the printing facility, the powder may be manually compacted using a hand stamper, preferably having a weight of 7 kg, that is dropped from a drop height of 1 to 3 cm in order to uniformly compact the filled material over the entire surface.

[0047] Both chambers 1, 5 preferably have the same base area; the base area of the powder storage chamber 1 may optionally be slightly larger than the base area of the construction chamber 5.

[0048] The two pistons 2 and 3 may each be moved in stages between 0.01 and 1.2 mm, for example between 0.1 and 1.0 mm, in particular by 0.6 mm, in the vertical direction, preferably in opposite vertical directions, via a stepping motor that is controlled from a controller board.

[0049] The powder bed thereby rises in the Z direction 4 in the powder storage chamber 1, by an appropriate degree beyond the edge of the print bed, and at the same time the construction chamber 5 lowers by an appropriate degree, in each case by the corresponding amount of 0.6 mm, for example.

[0050] A leveling roller 6 rotating clockwise at 5 to 30 rpm, preferably approximately 15 rpm, takes the topmost layer of the powder from the powder storage chamber 1 and distributes the powder uniformly on the base plate 7 of the construction chamber 5. After distributing a layer of the powder onto the construction chamber 5, the leveling roller 6 then travels back beyond the far side of the powder storage chamber 1. Due to the quasi-flow behavior of the powder, it may be necessary to briefly lower the construction chamber 5 and the powder storage chamber 1 during the return travel of the leveling roller 6 so that the leveling roller 6 does not push excess material over the edge of the print bed.

[0051] The mineral powder present in the construction chamber 5 is impacted by a laser beam 8 that is focused to a laser beam thickness between 0.1 and 1.0 mm via one or more focus lenses 9 connected in series, is heated at specific points, and sintered. The laser beam 10 is selectively guided in the X and Y directions, either by two linear guides or via a galvanic mirror having an F-theta objective lens, also referred to as a laser scanner 11.

[0052] After completion of the printing job for the first layer, which is possibly a support structure, optionally on a removable metal plate 12 with an adhesive coating up to 3 mm thick, preferably having a composition of 60 wt % sodium water glass, 30 wt % pre-expanded perlite that is ground for 1 h, and 10 wt % distilled water, the laser head or laser scanner 11 travels to its starting position.

[0053] The construction chamber 5 lowers once again in the Z direction by an amount between 0.01 and 1.2 mm, and the powder storage chamber 1 rises by the same amount. A further powder layer is applied by the leveling roller 6 and sintered by the laser beam 10. This operation is continued until the printing operation is completed.

[0054] The excess loose powder from the construction chamber 5 is removed using a suction device, and is sieved for the next printing application and combined with unused powder, depending on the amount of powder consumed, and prepared to ensure consistent quality.

[0055] The print object 13 is lifted from the construction chamber 5. The print object may possibly still adhere to the coated metal plate 12, in which case they are manually separated from one another at completion.

[0056] With the invention, it is possible to adjust selected subareas of the end product 13 in a targeted manner with regard to final strength, open porosity, and luminescence via a more or less intense degree of the energy input at specific points. FIG. 2 schematically illustrates the expanded powder 25 in layer 26, which is denser and more intensely sintered, while in layer 27 the powder is open-pored and melted less densely.

[0057] End products from previous selective laser sintering processes also have a maximum size with an approximately 65 cm edge length. In contrast, as the result of an increased production speed, based on a thicker powder application layer of up to 1.2 mm and better utilization of the absorption of the laser light, the invention is designed for end products having edge lengths of 0.5 mm to greater than 200 cm.

[0058] During the production process, fused silica may develop in the air space of the construction chamber, in particular due to localized evaporation of the raw starting material at the location of the laser sintering and/or in the area of the laser beam.

[0059] The fused silica that occurs in the air space of the construction chamber and/or in the area of the laser tubes may be collected by means of electrodeposition. This fused silica may then be marketed as a by-product independently of the actual print object, or used in some other way.

LIST OF REFERENCE NUMERALS

[0060] 1 raw starting material [0061] 2 first piston [0062] 3 second piston [0063] 4 Z direction [0064] 5 construction chamber [0065] 6 leveling roller [0066] 7 base plate [0067] 8 laser beam [0068] 9 focus lens [0069] 10 laser beam [0070] 11 laser scanner [0071] 12 metal plate [0072] 13 print object [0073] 23 expansion [0074] 25 expanded powder [0075] 26 dense layer [0076] 27 porous layer