CONDITIONED METAL PARTICLES FOR THREE-DIMENSIONAL PRINTING
Methods of preparing a particulate build material for three-dimensional printing can include loading fresh particulate build material including from about 80 wt % to 100 wt % fresh metal particles into a mechanical mixer, and mechanically conditioning the fresh particulate build material to generate conditioned particulate build material including conditioned metal particles. The fresh metal particles can have a surface oxide layer, and the fresh particulate build material can have a particle size distribution with a D10 particle size from about 2 μm to about 10 μm, a D50 particle size from about 5 μm to about 20 μm, and a D90 particle size from about 20 μm to about 40 μm. The conditioned particulate build material can include a modified cohesive index (compared to the fresh conditioned particulate build material) ranging from about 25 cohesive index units to about 35 cohesive index units.
1 . A method of preparing particulate build material for three-dimensional printing, comprising:
loading fresh particulate build material including from about 80 wt % to 100 wt % fresh metal particles into a mechanical mixer, wherein the fresh metal particles include a surface oxide layer, and wherein the fresh metal particles have a particle size distribution a D10 particle size from about 2 μm to about 10 μm, a D50 particle size from about 5 μm to about 20 μm, and a D90 particle size from about 20 μm to about 40 μm; and
mechanically conditioning the fresh particulate build material to generate conditioned particulate build material including conditioned metal particles, wherein the conditioned particulate build material has a modified cohesive index ranging from about 25 cohesive index units to about 35 cohesive index units.
2 . The method of claim 1 , wherein the metal particles include at least one of an elemental metal or alloy of iron, chromium, nickel, titanium, steel, stainless steel, carbon steel, cast iron, or wrought iron.
3 . The method of claim 1 , wherein the fresh metal particles are gas atomized spherical particles.
4 . The method of claim 1 , wherein mechanically conditioning occurs using at least one of an acoustic mixer, a convective mixer, a ribbon mixer, a tumbler mixer, a vertical mixer with a stirring mechanism, a pneumatic phase transport, a sieve, a hopper flow, or a tilt-table.
5 . The method of claim 1 , wherein mechanically conditioning occurs at about 2 RPM to about 60 RPM for a time period ranging from about 2 minutes to about 8 hours.
6 . The method of claim 1 , wherein mechanically conditioning occurs in the tumbler mixer or a vertical mixer at from about 10 RPM to about 25 RPM for a time period ranging from about 5 minutes to about 2 hours.
7 . A method of printing a three-dimensional object, comprising:
iteratively applying the conditioned particulate build material of claim 1 as individual build material layers to a powder bed; and
based on a 3D object model, selectively and iteratively applying a binding agent onto individual conditioned build material layers of the particulate build material to build up and bind the layers together to form a three-dimensional green body object.
8 . The method of claim 7 , further comprising sintering the three-dimensional green body object at an elevated temperature of from about 500° C. to about 3,500° C. to fuse the metal particles to one another and form a fused metal three-dimensional object.
9 . The method of claim 8 , wherein the fused metal three-dimensional object has a theoretical density from about 85% to 100%.
10 . The method of claim 8 , wherein the fused metal three-dimensional object has an elongation at break that is greater than a corresponding elongation at break of a comparable three-dimensional printed object formed identically except that the comparable three-dimensional object is prepared from the fresh particulate build material rather than the conditioned particulate build material.
11 . A three-dimensional printing kit, comprising:
a conditioned particulate build material including from 80 wt % to 100 wt % conditioned metal particles, wherein the conditioned particulate build material has a cohesive index ranging from about 25 cohesive index units to about 35 cohesive index units; and
a binding agent including an aqueous liquid vehicle and a binder.
12 . The three-dimensional printing kit of 11 , wherein the conditioned metal particles include gas atomized spherical stainless steel particles.
13 . The three-dimensional printing kit of claim 11 , wherein the binding agent is stable at 25° C., and the binder includes at least one of a polymer binder, a polymerizable binder, or thermally reducible metal salt or metal oxide nanoparticles in the presence of a reducing compound.
14 . A system for three-dimensional printing, comprising:
a conditioned particulate build material including from 80 wt % to 100 wt % conditioned metal particles having a cohesive index ranging from about 25 cohesive index units to about 35 cohesive index units; and
a printhead fluidly coupled to or fluidly coupleable to a binding agent to selectively and iteratively eject the binding agent onto successive applied individual layers of conditioned particulate build material.
15 . The system of claim 14 , further comprising a mechanical mixer to receive and condition fresh particulate build material to form the conditioned particulate build material including conditioned metal particles.