In an example of a method for three-dimensional (3D) printing, a build material composition is applied to form a build material layer. The build material composition includes a polymeric or polymeric composite build material, and a precipitating agent. Based on a 3D object model, a fusing agent is selectively applied on at least a portion of the build material composition. The fusing agent includes a radiation absorber, which the precipitating agent precipitates. The build material composition is exposed to radiation to fuse the at least the portion to form a layer of a 3D part.

In example implementations, a minor assembly for a three dimensional printer is provided. The minor assembly includes a first side and a second side. The first side is symmetrical to the second side and enclose a cylindrical light source. The first side and the second side each include a first curved reflective surface and a second curved reflective surface. An end of the first curved reflective surface and a beginning of the second curved reflective surface form an edge along a surface formed by the first curved reflective surface and the second curved reflective surface.

In example implementations, a minor assembly for a three dimensional printer is provided. The minor assembly includes a first side and a second side. The first side is symmetrical to the second side and enclose a cylindrical light source. The first side and the second side each include a first curved reflective surface and a second curved reflective surface. An end of the first curved reflective surface and a beginning of the second curved reflective surface form an edge along a surface formed by the first curved reflective surface and the second curved reflective surface.

An apparatus for 3D printing of the bottom-up photo-curing type, including an LCD light source with LED matrix, above which is positioned a tank containing a liquid photo-curing material, within which is immersed an extraction plate that moves with reciprocating rectilinear motion along a direction perpendicular to the bottom of the tank, from a position at a distance from the bottom of the tank equal to the thickness of a layer which can be obtained by photo-curing of said photo-curing liquid material, the bottom of the tank formed by an elastic membrane transparent to the radiation of said light source. The tank, light source and other components can be utilized in various methods of bottom-up photo-curing 3D printing, implemented using such an apparatus.

An apparatus for 3D printing of the bottom-up photo-curing type, including an LCD light source with LED matrix, above which is positioned a tank containing a liquid photo-curing material, within which is immersed an extraction plate that moves with reciprocating rectilinear motion along a direction perpendicular to the bottom of the tank, from a position at a distance from the bottom of the tank equal to the thickness of a layer which can be obtained by photo-curing of said photo-curing liquid material, the bottom of the tank formed by an elastic membrane transparent to the radiation of said light source. The tank, light source and other components can be utilized in various methods of bottom-up photo-curing 3D printing, implemented using such an apparatus.

In one example, a lighting device for an additive manufacturing machine includes an array of light sources each to emit monochromatic light within a band of wavelengths that includes a peak light absorption of a liquid coalescing agent to be dispensed on to a build material.

According to an example, a composition may include a high melt temperature build material in the form of a powder; a first low melt temperature binder in the form of a powder; and a second low melt temperature binder in the form of a powder; and in which the first low melt temperature binder melts at a temperature that is different from the second low melt temperature binder.

According to an example, a composition may include a high melt temperature build material in the form of a powder; a first low melt temperature binder in the form of a powder; and a second low melt temperature binder in the form of a powder; and in which the first low melt temperature binder melts at a temperature that is different from the second low melt temperature binder.

An example apparatus to produce a three-dimensional object comprises a controller, a build area configured to receive a layer of particulate material, a printhead, and an ultraviolet light emitting diode energy source. The controller is to cause the printhead to deposit a liquid which absorbs ultraviolet radiation onto the layer of particulate material. The controller is further to cause the ultraviolet light emitting diode energy source to irradiate the liquid, after the liquid has been deposited onto the layer of particulate material, thereby to heat the liquid and cause a portion of the particulate material to solidify.

An example apparatus to produce a three-dimensional object comprises a controller, a build area configured to receive a layer of particulate material, a printhead, and an ultraviolet light emitting diode energy source. The controller is to cause the printhead to deposit a liquid which absorbs ultraviolet radiation onto the layer of particulate material. The controller is further to cause the ultraviolet light emitting diode energy source to irradiate the liquid, after the liquid has been deposited onto the layer of particulate material, thereby to heat the liquid and cause a portion of the particulate material to solidify.