Device and a method for fabricating a three-dimensional part by selectively melting a powder bed

A method of fabricating a three-dimensional part by selectively melting a powder bed, the part comprising a successive stack of layers, the method comprising the following steps for fabricating one layer:

• a) delivering a monitored quantity of a first powder from a first tank;
• b) delivering a monitored quantity of a second powder different from the first powder from a second tank;
• c) mixing the first powder and the second powder as delivered in steps a) and b);
• d) depositing a layer of the mixture of the first powder and the second powder obtained in step c);
• and
• e) melting at least a portion of the layer of the mixture deposited in step d),
• wherein the first powder presents a first grain size and the second powder presents a second grain size, the first grain size being different from the second grain size,
• wherein the mixing at step c) comprises:
• mixing the first powder and the second powder within a mixer chamber, the mixing chamber comprising an inlet orifice and an outlet orifice for a gas stream inside the mixer chamber, said gas stream inlet and outlet orifices being configured to cause a gas to flow in the mixer chamber so as to mix the first powder and the second powder contained in said mixer chamber, and
• wherein the outlet orifice has a protection cover configured to prevent powder from escaping from the mixer chamber via said outlet orifice, and said method further comprising preventing powder from escaping from the mixer chamber via said outlet orifice using the protection cover.