System and method for improving mechanical properties of polymer powder bed fusion processes
Sintering methods comprising (a) providing a layer of powder material on a platform; (b) projecting incident light from a source onto a surface area of the layer of powder material, wherein the incident light is projected for a sufficient time to densify the layer of powder material and form a layer of densified material; (c) optionally cooling the layer of densified material to a sufficient temperature to solidify or vitrify the layer of densified material to form a layer of sintered material; and (d) repeating steps (a) to (c) to form a sintered article in a layer-wise fashion are disclosed. The incident light may cause complete melting of the powder material or heat the powder material above its glass transition temperature. In general, the incident light is projected simultaneously and for a time span substantially the same as formation of the layer of densified material.
1 . A sintering method comprising:
(a) providing a layer of powder material on a platform; wherein the powder material is not a metal and comprises a polymer;
(b) projecting an incident light from a source onto a surface area of the layer of powder material, wherein the incident light is projected for a sufficient time to densify the layer of powder material and form a layer of densified material, and wherein densifying the layer of powder material comprises melting the powder material, and wherein an area of the incident light projected on the surface of the layer of powder material and a thickness of the layer of powder material are in a ratio of at least 30:1, wherein the incident light is projected at a power level from 1 W/cm 2 to 50 W/cm 2 ;
(c) cooling the layer of densified material to below its recrystallization temperature to solidify the layer of densified material to form a layer of sintered material; and
(d) repeating steps (a) to (c) to form a sintered article in a layer-wise fashion,
wherein the article comprises greater than one layer of sintered material; and
wherein the powder material is premixed with a radiation absorber prior to step (a).
2 . The method of claim 1 , further comprising maintaining the platform at an elevated temperature below an initial melting temperature or glass transition temperature of the powder material and/or pre-heating the surface of the layer of powder material prior to step (b).
3 . The method of claim 1 , wherein the powder material further comprises a ceramic or a composite material.
4 . The method of claim 1 , wherein the polymer is selected from a polyamide, a polystyrene, a polyester, a polyacetal, a polyalkylene, cellulose, a poly ether ether ketone, a poly ether ketone, a poly ether ketone ketone, a poly (meth)acrylate, a polyimide, a thermoplastic urethane, a polyether, a polyketone, a polycarbonate, a thermoplastic elastomer, a polyolefin, a copolyester, a thermoplastic vulcanite, a polyethene, a polystyrene, a poly vinyl chloride, a blend thereof, a copolymer thereof, or a derivative thereof.
5 . The method of claim 1 , wherein the powder material comprises particles having an average particle diameter of from 5 to 250 microns.
6 . The method of claim 1 , wherein the layer of powder material has a thickness of from 10 microns to 1 mm.
7 . The method of claim 1 , wherein the source is selected from an image projector, an array of LED or laser, or an effectively constant exposure obtained by repeatedly scanning the incident light at high rate of speed over the surface of the powder material.
8 . The method of claim 1 , wherein the incident light is projected for a time span the same as formation of the layer of densified material having less than 5% by volume pores, as determined by the Archimedes density test.
9 . The method of claim 1 , wherein step (c) comprises cooling the layer of sintered material by exposure to ambient temperature, exposure to a cool air stream, depositing a cooler material on the layer of densified material, or in a thermally controlled chamber at a cooling rate of at least 1° C./min.
10 . The method of claim 1 , further comprising fusing individual subsections having an area of at least 3.36 cm 2 or an entire area of the sintered article and allowing each subsection or area to cool to form a 3D sintered article.
11 . The method of claim 1 , wherein the sintered article comprises less than 2% by volume pores, as determined by the Archimedes density test.
12 . The method of claim 1 , wherein the densified material is cooled at a rate of greater than 10° C./min, in step (c).
13 . The method of claim 1 , comprising heating a 2D area that is at least 3.36 cm 2 for a time span the same as formation of the layer of densified material having less than 5% by volume pores, as determined by the Archimedes density test.
14 . The method of claim 1 , wherein the powder material comprises a semi-crystalline polymer or amorphous polymer.
15 . The method of claim 1 , wherein the sufficient time is from 100 ms to 30 s.