3D-Metal-Printing Method and Arrangement Therefor

Abstract

The invention relates to a 3D-metal-printing method for producing a spatial metal product substantially consisting of a metal powder or metal filaments, the powder or the filaments being structured layer-by-layer by application of starting material layers to a respectively previously produced layer and selective local heating of predefined points of the layer above a sintering or melting temperature of the powder and fusion of the molten points with the underlying layer and optional tempering of the points, in which the respectively newly applied starting material layer and optionally at least one underlying layer are preheated by planar or migratory irradiation of near-IR radiation, particularly with a maximum radiation density in the wavelength range of between 0.8 and 1.5 m, to a temperature with a predetermined difference to the melting temperature and/or points predefined in connection with the local heating are subjected to an aftertreatment for thermal voltage compensation.

Claims

1. 3D-metal-printing method for producing a spatial metal product essentially from a metal powder or metal filaments, wherein the powder or the filaments is/are built up layer-by-layer by applying starting material layers to a respective previously produced layer and selectively locally heating predetermined points of the layer above a sintering or melting temperature of the powder and sintering or fusing the melted points with the underlying layer and optionally tempering the points, wherein the respective newly applied starting material layer and optionally at least one underlying layer is preheated to a temperature with a predetermined difference to the melting temperature by irradiation in a flat or migrating manner of near IR radiation, in particular with a radiation density maximum in the wavelength range between 0.8 and 1.5 m, and/or is post-treated following the local heating of predetermined points for thermal stress equalization.

2. 3D-metal-printing method according to claim 1, wherein the near IR radiation is sequentially irradiated in sections into partial sections of the total area of the respective starting material layer, wherein the selective local heating above the sintering or melting temperature is carried out in each case for predetermined points within a preheated partial section.

3. 3D-metal-printing method according to claim 1, wherein the power density of the near IR radiation irradiated over a surface is above 1 MW/m.sup.2.

4. 3D-metal-printing method according to claim 1, wherein the radiation of at least one halogen radiator, in particular a plurality of halogen radiators, with a radiator temperature in particular also in the range of 2900 K to 3200 K is used as near IR radiation.

5. 3D-metal-printing method according to claim 1, wherein the selective local heating of predetermined points is affected by scanning the starting material layer with an electron or laser beam.

6. 3D-metal-printing method according to claim 1, wherein preheating to a material-specific preset temperature, in particular in the range between 600 and 1100 C., more particularly in the range between 700 and 1000 C., is carried out and is controlled in particular by time and/or radiation density control of the irradiation of the near IR radiation.

7. A system for 3D metal printing, comprising: a worktable as a base for layer-by-layer structure of a spatial metal product, a powder application device for sequential application of starting material layers of a metal powder or starting material filaments in the area of the worktable, a surface heating device for surface heating of each new starting material layer for preheating or thermal post-treatment, the surface-heating device having an NIR irradiation device for irradiating near IR radiation, in particular with a radiation density maximum in the wavelength range between 0.8 and 1.5 m, onto a predetermined surface in the region of the worktable, and a mechanism providing selective local heating of predetermined points of the new starting material layer above a sintering or melting temperature of the metal powder.

8. System according to claim 7, wherein the mechanism providing selective local heating of predetermined points of a previously applied starting material layer comprises a laser with a downstream scanner for point-by-point irradiation of near NIR radiation or visible light in the long-wave range onto the predetermined points.

9. System according to claim 7, wherein the mechanism providing selective local heating of predetermined points of a previously applied starting material layer comprises an electron beam generator for the point-by-point irradiation of electron radiation onto the predetermined points, and the arrangement is arranged in a vacuum chamber subjected to a high vacuum.

10. System according to claim 7, wherein the NIR irradiation device comprises at least one halogen radiator, in particular a plurality of halogen radiators, with a reflector associated such that the radiation of the or each infrared radiator is concentrated in the direction towards the worktable.

11. System according to claim 10, wherein the halogen radiator or the plurality of halogen radiators with associated reflector is mounted above the worktable so as to be movable in at least one axial direction of an XY plane.

12. System according to claim 10, wherein the halogen radiator or radiators is/are designed for operation at a radiator temperature in the range of 2900 K to 3200 K.

Description

[0026] The advantages and usefulness of the invention are further explained in the following description of an embodiment example using the figures, wherein:

[0027] FIG. 1 shows a schematic representation, in the manner of a longitudinal section, of an arrangement and a method according to an embodiment of the invention,

[0028] FIG. 2 shows a schematic representation, in the manner of a longitudinal section, of an arrangement and a method according to a further embodiment of the invention, and

[0029] FIG. 3 shows a schematic representation, in the manner of a longitudinal section, of an arrangement and a method according to a further embodiment of the invention.

[0030] FIG. 1 shows a sketch-like arrangement 100 for the additive production of a (here still incompletely shown) spatial metal product P, which is formed from a metal powder bed 101 by means of layer-by-layer application of metal powder and scanning local heating of the individual layers.

[0031] The arrangement comprises a worktable 103, on which the metal powder bed 101 is applied layer-by-layer and the metal product P is formed. As symbolized by the arrow A, the worktable 103 can be moved vertically in order to keep the surface of the metal powder bed 101 at the same height level despite the fact that the height increases with the layer application. A powder application device for feeding metal powder into the actual working area comprises a punch 105, which is vertically movable in the direction of the arrow B, i.e. in the opposite direction to arrow A, and a powder application roller 107, which is movable in the direction of arrow C and moves metal powder 109 received as a supply on the punch 105 in individual layers of predetermined thickness into the working area (i.e. in the figure to the right into the powder bed 101).

[0032] An NIR radiation source 111, which in the example is formed by a single halogen lamp and an associated reflector 111b, is positioned above the working area. The NIR radiation source 111, as symbolized by the arrows D1 and D2, can be moved laterally back and forth across the powder bed 101 and serves to preheat the respectively irradiated sections of the powder bed to a temperature below a sintering or melting temperature of the metal powder. Optionally, it can also be used for thermal post-treatment (annealing) of a layer that has been locally melted immediately before, which can be carried out, for example, by retracting the NIR radiation source in the direction of arrow D2, if the radiation source has been moved over the surface of the powder bed 101 in the direction of arrow D1 for preheating. The NIR radiation source 111 can also comprise several halogen lamps with a reflector that is then shaped accordingly.

[0033] A commercial processing laser 113, selected with regard to the absorption properties of the metal powder to be processed and of course under cost aspects, with a downstream scanner 115 is arranged above the working area. The laser 113 and scanner 115 are designed in such a way that the surface of the powder bed 101 can be scanned with a laser beam L in order to heat the powder bed 101, which is preheated by the NIR radiation on its surface, above the sintering or melting temperature at the points of impact predetermined according to the product geometry. This causes a sintering with the respectively underlying layer at those points, thus forming the next layer of the metal product P. In a method control specific to the structure of certain metallic products, in a second scanning pass with the laser radiation already used for sintering or melting, an annealing of the sintered or fused areas is carried out to set desired mechanical properties. However, as mentioned above, this step can be replaced according to the invention by a stationary or migrating irradiation of the uppermost material layer with NIR radiation.

[0034] In the usual way, the metal powder 109 remains in the powder state in those places where it has not been heated above the sintering or melting temperature and, after removal from the worktable, falls off the metal product P or can be washed out of it.

[0035] FIG. 2 shows an arrangement 100 which is very similar to arrangement 100 according to FIG. 1, in which the matching parts are marked with the same reference numbers as in FIG. 1 and are not explained again here. The essential difference to arrangement 100 is that instead of a laterally movable NIR irradiation device, a stationary NIR irradiation device 111 with a simple large-area reflector 111b and a row of halogen lamps 111a arranged below is provided here. It is understood that the relative arrangement of laser 113 and scanner 115 on the one hand and the NIR irradiation device 111 on the other hand must be determined in such a way that the radiation from both radiation sources can reach the entire surface of the powder bed 101 to be processed unhindered.

[0036] FIG. 3 also shows an arrangement 100 which is partly similar to the arrangement according to FIG. 1. In this case too, the parts corresponding to FIG. 1 are marked with the same reference numbers as there. The arrangement 100 is configured as an EBM processing arrangement, i.e. instead of a processing laser and the associated scanner, an electron beam tube 113 with associated coordinate-controlled deflection unit 115 is used.

[0037] The deflection unit 115 deflects an electron beam E generated by the electron beam tube 113 to any points on the surface of the powder bed 101, which are defined by production drawings of the metal product P with regard to its individual layers. By means of a power operating current control (not shown) of the electron tube 113, the power of the electron beam E and thus the temperature attainable at the point of impact can be controlled almost without inertia. This enables, among other things, the precise T-controlled execution of sintering or melting steps on the one hand and subsequent tempering steps of the applied metal layer on the other hand.

[0038] In addition, the entire arrangement is housed here in a vacuum chamber 117, to which a vacuum generator 119 is assigned to generate a high vacuum in the vacuum chamber during the manufacturing process of a product.

[0039] With regard to the use and the constructive design of the NIR radiation source 111, reference is hereby made to the corresponding embodiments in FIG. 1. At present, it is considered advantageous to place the NIR radiation source 111 in the vacuum chamber 117 as well; in principle, however, the radiator module could also be placed outside the vacuum chamber and the NIR radiation directed onto the product surface through an NIR-permeable window and, optionally, corresponding mirrors.

[0040] Furthermore, the embodiment of the invention is also possible in a number of variations of the examples shown here and aspects of the invention highlighted above.