Method and apparatus for producing three-dimensional objects

1. A process for manufacturing a three-dimensional object by successive layer-by-layer consolidation of selected zones of a powder stratum, the consolidated zones corresponding to successive sections of the three-dimensional object, each layer being divided into a central internal portion and an external border, comprising, in order:

a—depositing a powder layer on a holder;

b—fusing the external border of said powder layer by means of a laser beam originating from a first energy source by moving the laser beam of said first energy source relative to the object along a preset path that follows the contour of said external border corresponding to the contour of the cross section of the object so as to selectively fuse said layer; and

c—fusing the central internal portion of the powder layer by means of an electron beam originating from a second energy source, by moving the electron beam of said second energy source relative to the object so as to sweep it over said central internal portion along a preset path corresponding to the central internal portion of the cross section of the object so as to selectively fuse said layer; or

d—repeating steps a and b N times so as to form a plurality of superposed layers of fused material forming a portion of the external border of said object and then carrying out step c so as to fuse the central internal portion of the object corresponding to the N powder layers; and

e—repeating steps a to c or a, b and d until all the layers of the object have been consolidated.

2. The process according to claim 1 , wherein, for a given section, the width of said external border is at most 1 mm.

3. The process according to claim 1 , wherein the fusion by the laser beam starts in a zone distant from the center of the object, and the fusion by the electron beam starts in a zone near the center of the object.

4. The process according to claim 1 , further comprising an additional step of fusion by the laser beam of an internal border or of a bead arranged in the central internal portion.

5. The process according to claim 1 , wherein a ratio between energy delivered by the electron beam and energy delivered by the laser beam is between 4:1 and 9:1.

6. The process according to claim 1 , wherein the powder is composed of particles that have an average diameter between 5 μm and 300 μm.

7. The process according to claim 1 , wherein said central internal portion has an open structure.

8. The process according to claim 1 , further comprising at least one additional step of preheating the powder layer using at least one of said first or second energy sources.

9. The process according to claim 1 , further comprising an additional step of finishing the central internal portion and the external border of the object by fusing the last powder layer using the laser beam.

10. The process according to claim 1 , wherein the specific power of the electron beam is between 2×10 6 and 50×10 6 W/cm 2 .

11. The process according to claim 1 , wherein the specific power of the laser beam is between 200 and 2400 kW/cm 2 .

12. The process according to claim 1 , wherein said powder is a metal powder.

13. The process according to claim 1 , wherein a focal point of the electron beam is located above a surface of said powder layer.

14. The process according to claim 1 , wherein the powder layer and the first and second energy sources are in a vacuum.

15. The process according to claim 14 , wherein the vacuum has a pressure in the range of 10 −4 to 10 −6 mbar.

16. The process according to claim 1 , wherein the second energy source is held stationary and wherein the electron beam is moved relative to the object by deflecting the electron beam with deflecting coils.