Abstract: A three-dimensional printing build material composition includes a polymer particle, and a radiation absorbing additive mixed with the polymer particle. The radiation absorbing additive has a particle size ranging from about 1 ?m to about 100 ?m, and the radiation absorbing additive is to absorb incident radiation having wavelengths ranging from 700 nm to 10 ?m.

Abstract: A printed object includes a modification not present in the original model of the object. The modification is included in a base layer of the object.

Abstract: The present disclosure is drawn to material sets for 3D printing and methods of 3D printing. The material set can include a coalescent an organic-soluble near-infrared dye having a peak absorption wavelength from 800 nm to 1400 nm. The coalescent ink can also include water and an organic co-solvent. The material set can also include a particulate polymer formulated to coalesce when contacted by the coalescent ink and irradiated by a near-infrared energy having the peak absorption wavelength.

Abstract: The present disclosure is drawn to powder bed materials. The powder bed material can include from 20 wt % to 95 wt % of a large particulate metal and from 5 wt % to 80 wt % of a small particulate metal. The large particulate metal can have a D50 particle size distribution value ranging from 20 ?m to 100 ?m and an average aspect ratio from 1:1 to 1.1:1. The small particulate metal can have a D50 particle size distribution value ranging from 1 ?m to 15 ?m and an average aspect ratio from greater than 1.1 to 2.1.

Abstract: The present disclosure is drawn to coalescent inks and material sets for 3D printing. The coalescent ink can include an organic-soluble near-infrared dye having a peak absorption wavelength from 800 nm to 1400 nm. The coalescent ink can also include water and an organic co-solvent.

Abstract: In one example, a non-transitory processor readable medium with instructions thereon that when executed cause an additive manufacturing machine to partially or completely bury a part in layers of molten build material.

Abstract: The present disclosure is drawn to coalescent inks and material sets for 3D printing. The coalescent ink can include a water-soluble near-infrared dye having a peak absorption wavelength from 800 nm to 1400 nm. The coalescent ink can also contain water.

Abstract: In one example, a non-transitory processor readable medium having instructions thereon that when executed cause an additive manufacturing machine to expose build material to a light source emitting monochromatic light within a band of wavelengths that includes a peak light absorption of a liquid coalescing agent to be dispensed on to the build material.

Abstract: A polymeric powder composition for three-dimensional printing includes first, second, and third polymeric particles. The first particles, having a first average size, are present in an amount ranging from about 70 wt % to about 95 wt %. The second particles, having a second average size smaller than the first average size, are present in an amount ranging from about 0.5 wt % to about 21 wt %. The third particles, having a third average size smaller than the second average size, are present in an amount ranging from greater than 0 wt % up to about 21 wt %. Each of the first, second, and third average sizes independently ranges from 5 ?m to about 100 ?m. A sum of the fractional weight ratios of all of the polymeric particles in the polymeric powder composition equals 1.

Abstract: A system including: a polymer substrate with a thermal conductivity of less than 0.5 W/(m-k); a spreader to form a layer of metal particulate on the polymer substrate; a mask applicator to apply a mask to a portion of the layer of metal particulate; and a pulsed irradiation light source to fuse a portion of the layer of metal particulate not covered by the mask.

Abstract: Provided in one example herein is a three-dimensional (“3D”) printing method, comprising: (A) forming a layer comprising particles comprising a thermoplastic; (B) disposing over at least a portion of the layer a coalescent agent, which is radiation-absorbing and has a thermal decomposition temperature lower than or equal a melting temperature of the thermoplastic; (C) forming an object slice of a 3D object by exposing the coalescent agent to a radiant energy such that at least some of the coalescent agent thermally decomposes while causing at least some of the particles to fuse, wherein the object slice comprises the fused particles, and wherein the thermally decomposed coalescent agent is not radiation-absorbing; and (D) repeating (A) to (C) to form the 3D object comprising multiple object slices bound depth-wise to one another.

Abstract: In a computational modeling method for identifying how to apply a modifying agent during a three-dimensional (3D) printing method, a thermal diffusion model of a layer of a 3D object to be formed from a portion of a sinterable material using the 3D printing method is created. The thermal diffusion model is created by a computer running computer readable instructions stored on a non-transitory, tangible computer readable storage medium. A quantity of the modifying agent to be selectively applied is calculated, by the computer, based upon the thermal diffusion model.

Abstract: In a 3D printing method, a sinterable material is applied and heated to a temperature ranging from about 50° C. to about 400° C. A coalescent agent is selectively applied on a portion of the sinterable material, and a modifying agent is selectively applied on the portion and/or on another portion of the sinterable material. The modifying agent consists of an inorganic salt, a surfactant, a co-solvent, a humectant, a biocide, and water. The sinterable material is exposed to radiation, whereby the coalescent agent at least partially cures the portion of the sinterable material in contact with the coalescent agent, and the modifying agent i) reduces curing of the portion of the sinterable material in contact with both the coalescent agent and the modifying agent ii) prevents curing of the other portion of the sinterable material in contact with the modifying agent, or iii) both i and ii.

Abstract: Apparatus and methods for making metal-connected particle articles. A metal containing fluid is selectively applied to a layer of particles. The metal in the fluid is used to form metal connections between particles, The metal connections are formed at temperatures below the sintering temperature of the particles in the layer of particles.

Abstract: Apparatus and methods for making metal-connected particle articles. A metal containing fluid is selectively applied to a layer of particles. The metal in the fluid is used to form metal connections between particles. The metal connections are formed at temperatures below the sintering temperature of the particles in the layer of particles.

Abstract: Apparatus and methods for making metal-connected particle articles. A metal containing fluid is selectively applied to a layer of particles. The metal in the fluid is used to form metal connections between particles. The metal connections are formed at temperatures below the sintering temperature of the particles in the layer of particles.

Abstract: In one example, an apparatus for generating a three-dimensional object includes an energy source to apply energy to a layer of build material to cause a first portion of the layer to coalesce and solidify, an agent distributor to selectively deliver a cooling agent onto a second portion of the layer, and a controller to control the energy source to apply energy to the layer to cause the first portion to coalesce and solidify in a first pattern and to control the agent distributor to selectively deliver the cooling agent onto the second portion of the layer in a second pattern independent of the first pattern.

Abstract: To additively manufacture a 3D object, a layer of material is deposited onto a receiving surface. Droplets are selective deposited onto first portions of the layer with at least some droplets including at least a first color agent. A gas discharge illuminant selectively induces a first amount of heating in the first portions of the layer substantially greater than a second amount of heating in second portions of the layer omitting the first color agent.

Abstract: In a three-dimensional printing method example, a metallic build material is applied. A positive masking agent is selectively applied on at least a portion of the metallic build material. The positive masking agent includes a radiation absorption amplifier that is compatible with the metallic build material. The metallic build material is exposed to radiation from a spatially broad, high energy light source to melt the portion of the metallic build material in contact with the positive masking agent to form a layer. The radiation absorption amplifier i) has an absorbance for the radiation that is higher than an absorbance for the radiation of the metallic build material, or ii) modifies a surface topography of the at least the portion of the metallic build material to reduce specular reflection of the radiation off of the at least the portion of the metallic build material, or both i) and ii).

Abstract: According to an example, an apparatus may include a heating lamp to illuminate and heat an area of a layer of build materials, in which the build materials may be one of a metallic and a plastic powder. The apparatus may also include a laser source to generate a laser beam and a controller to control the heating lamp to heat the build materials in the area of the layer of build materials to a temperature that is between about 100 C to about 400 C below a temperature at which the build materials begin to melt and to control the laser source to output a laser beam to melt the build materials in a portion of the heated area of the layer of build materials.