3D-Metal-Printing Method and Arrangement Therefor

Abstract

3D metal printing process for producing a spatial metal product essentially from a metal powder or metal filaments as starting material, the powder or the filaments being built up layer by layer by applying layers of starting material to a respective previously produced layer and selective local heating of predetermined points of the layer above a sintering or melting temperature of the powder and sintering or fusing of the molten points with the underlying layer and optional annealing of the points. wherein at least the respective newly applied starting material layer is pre-heated and/or post-treated for thermal stress compensation following the local heating of the predetermined points by means of two-dimensional irradiation of IR radiation in such a way that a radiation spot with an area of at least 5 mm2, more particularly of more than 20 mm2 and even more particularly of more than 100 mm2, is formed on the surface of the starting material layer.

Claims

4. 3D metal printing process 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 in the range from 2900 K to 3200 K, is used as IR radiation.

5. 3D metal printing process according to claim 1, wherein more than one rod-shaped IR emitter, in particular halogen emitter, with associated reflector is used to produce a narrow rectangular radiation spot.

6. 3D metal printing process according to claim 1, wherein the selective local heating of predetermined points is effected by scanning the starting material layer with an electron beam.

7. 3D metal printing process according to claim 1, wherein each deposited source material layer has a thickness of at least 150 □m, more particularly of more than 300 □m and still more particularly of more than 500 □m, and is heated through its full thickness by the IR radiation.

8. A system for performing a 3D metal printing process for producing a spatial metal product essentially from a metal powder or metal filaments as a starting material, comprising: a work table as a base for building up the spatial metal product layer by layer, a powder application device for sequentially applying starting material layers of a metal powder or starting material filaments in an area of the work table, a surface heating device for surface heating of each new starting material layer, and for pre-heating or thermal post-treatment, the surface heating device comprising an IR irradiation device for generating a radiation spot having an area of at least 5 mm2, more particularly of more than 20 mm2 and even more particularly of more than 100 mm2, wherein the power density of the IR radiation irradiated over the surface of the starting material layer is above 1 MW/m2, and apparatus for effecting selective local heating of predetermined points of the new starting material layer above a sintering or melting temperature of the metal powder.

9. The system according to claim 8, wherein the apparatus for effecting selective local heating of predetermined points of a pre-applied layer of starting material comprise an electron beam generator for point-by-point irradiation of electron radiation to the predetermined points, and the apparatus further comprises a vacuum chamber subjected to high vacuum.

10. The system according to claim 8, wherein the IR irradiation device comprises at least one IR-irradiator, in particular halogen irradiator, with a reflector associated and formed in such a way that the radiation of each infrared irradiator is concentrated in the direction of the work table and the radiation spot has an area of at least 5 mm2, more particularly of more than 20 mm2 and even more particularly of more than 100 mm2 is formed on the last layer of starting material.

11. The system according to claim 10, wherein the IR irradiator or a plurality of IR irradiators with associated reflector is movably mounted above the work table in at least one axial direction of an XY plane.

12. The system according to claim 10 or 11, wherein the halogen radiator(s) operate with a radiator temperature in the range of 2900 K to 3200 K.

13. The system according to claim 10, wherein the IR irradiation device is equipped with at least one rod-shaped IR radiator, in particular halogen radiator, the length of which corresponds to at least one dimension of the metal product to be produced, and comprises a device for moving the IR radiator in exactly one axial direction of the XY plane.

14. The system according to claim 9, further comprising a heating control device which is connected via control outputs to the surface heating device and the apparatus for effecting selective local heating and controls both in accordance with a heating control program such that a temperature in a predetermined temperature range is maintained in the new starting material layer for a predetermined period of time.

Description

[0040] FIG. 1 shows a sketch of an arrangement 100 for additive manufacturing of a spatial metal product P (not yet shown in full here), which is formed from a metal powder bed 101 by applying metal powder layer by layer and locally heating the individual layers by scanning.

[0041] The arrangement comprises a work table 103 on which the metal powder bed 101 is applied layer by layer and the metal product P is formed. As symbolised by the arrow A, the work table 103 is vertically movable in order to keep the surface of the metal powder bed 101 at the same height level despite its increasing height as the layer application progresses.

[0042] A powder application device for feeding metal powder into the actual working area comprises a punch 105, which can be moved vertically in the direction of arrow B, i.e. in the opposite direction to arrow A, and a powder application blade 107, which can be moved in the direction of arrow C and displaces metal powder 109, which is accommodated on the punch 105 as a supply, in each case in individual layers of predetermined thickness into the working area (i.e. in the FIGURE to the right into the powder bed 101). It should be noted that the means for successively applying layers of powder to the work table the metal powder bed 101 formed there are shown in the FIGURE only by way of example and symbolically; the actual execution of this work step in the context of the realisation of the invention can be carried out according to established techniques.

[0043] An NIR radiation source 111, which in the example constitutes of a single halogen lamp 111a and an associated reflector 111b, is positioned above the working area. The NIR radiation source 111 can be moved laterally back and forth over the powder bed 101, as symbolised by the arrows D1 and D2, 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 is also used for thermal annealing of a locally melted layer immediately beforehand, which can be done, for example, by “moving back” 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 pre-heating. The NIR radiation source 111 can also comprise several halogen lamps with a reflector that is then shaped accordingly.

[0044] An electron beam tube 113 with associated coordinate-controlled deflection unit 115 is arranged above the working area. The deflection unit 115 directs an electron beam E generated by the electron beam tube 113 to any points on the surface of the preheated powder bed 101, which are predetermined by production drawings of the metal product P with regard to its individual layers. The electron beam heats the powder bed 101, which is preheated on its surface by the NIR radiation, above the sintering or melting temperature at the impact points predetermined according to the product geometry. This causes sintering with the respective underlying layer at those points and thus the next layer of the metal product P is formed. In the usual manner, the metal powder 109 remains in the powder state at those points where it has not been heated above the sintering or melting temperature and falls off the metal product P after removal from the work table or can be washed out of it.

[0045] By means of a (not shown) power operating current control of the electron tube 113, the power of the electron beam E and thus the achievable temperature at the point of impact can be controlled almost without delay. This enables, among other things, the precise T-controlled execution of sintering or melting steps on the one hand and subsequent annealing steps of the applied metal layer on the other hand.

[0046] The entire arrangement is housed in a vacuum chamber 117, which is associated with a vacuum generator 119 for generating a high vacuum in the vacuum chamber during the manufacturing process of a product.

[0047] Moreover, the invention can also be implemented in a variety of variations of the example shown here and aspects of the invention highlighted above.