Three-dimensional printing

Abstract

In an example of a method for three-dimensional (3D) printing, build material layers are patterned to form an intermediate structure. During patterning, a binding agent is selectively applied to define: a build material support structure and a patterned intermediate part. Also during patterning, i) the binding agent and a separate agent including a gas precursor or ii) a combined agent including a binder and the gas precursor are selectively applied to define a patterned breakable connection between at least a portion of the build material support structure and at least a portion patterned intermediate part. The intermediate structure is heated to a temperature that activates the gas precursor to create gas pockets in the patterned breakable connection.

What is claimed is: 
     
         1 . A method for three-dimensional (3D) printing, comprising:
 patterning build material layers to form an intermediate structure, the patterning including:
 selectively applying a binding agent to define: a build material support structure and a patterned intermediate part; and 
 selectively applying i) the binding agent and a separate agent including a gas precursor or ii) a combined agent including a binder and the gas precursor to define a patterned breakable connection between at least a portion of the build material support structure and at least a portion of the patterned intermediate part; and 
   heating the intermediate structure to a temperature that activates the gas precursor to create gas pockets in the patterned breakable connection.   
     
     
         2 . The method as defined in  claim 1  wherein the heating involves exposure to a series of temperatures that form:
 a 3D object from the patterned intermediate part; 
 a 3D support structure from the build material support structure; and 
 an irreversibly breakable connection from the patterned breakable connection, the irreversibly breakable connection including the gas pockets and being positioned between the 3D object and the 3D support structure. 
 
     
     
         3 . The method as defined in  claim 2  wherein the heating involves:
 heating the intermediate structure to a de-binding temperature; and 
 then heating the intermediate structure to an initial sintering temperature, followed by a gas pocket formation temperature, followed by a final sintering temperature. 
 
     
     
         4 . The method as defined in  claim 2 , further comprising removing the 3D support structure from the 3D object by breaking the irreversibly breakable connection. 
     
     
         5 . The method as defined in  claim 1  wherein the patterned intermediate part at least partially overlies the build material support structure. 
     
     
         6 . The method as defined in  claim 1  wherein patterning the build material layers includes:
 patterning a first build material layer by selectively applying the binding agent to define: a layer of the build material support structure and a layer of the patterned intermediate part separated by non-patterned build material; 
 applying an other layer of build material on the patterned first build material layer; 
 patterning the other layer of build material by:
 selectively applying i) the binding agent and the separate agent or ii) the combined agent on a portion of the other layer of build material that overlies the build material support structure, thereby forming the patterned breakable connection; and 
 selectively applying the binding agent on an other portion of the other layer of build material to define an outer layer of a region of the patterned intermediate part; and 
 
 forming a remaining region of the patterned intermediate part on the patterned breakable connection and in contact with the region of the patterned intermediate part, thereby forming the intermediate structure including the patterned intermediate part and the build material support structure temporarily bound together at the patterned breakable connection. 
 
     
     
         7 . The method as defined in  claim 6  wherein the build material support structure is a multi-layer structure, and wherein prior to patterning the other layer of build material the method further comprises iteratively applying additional build material layers and selectively applying the binding agent to the additional build material layers to define several layers of the build material support structure and several layers of the region of the patterned intermediate part, wherein the several layers of the build material support structure and the several layers of the region of the patterned intermediate part are separated by additional non-patterned build material. 
     
     
         8 . The method as defined in  claim 7  wherein the forming of the remaining region of the patterned intermediate part includes:
 applying a further layer of build material on the patterned breakable connection and the outer layer of the region of the patterned intermediate part; and 
 selectively applying the binding agent to the further layer to define a patterned layer of the remaining region of the patterned intermediate part. 
 
     
     
         9 . The method as defined in  claim 1  wherein patterning the build material layers includes:
 iteratively applying individual build material layers; 
 selectively applying the binding agent to each of the individual build material layers to define several layers of the build material support structure and several layers of the patterned intermediate part; and 
 selectively applying the i) the binding agent and the separate agent or ii) the combined agent on each of the individual build material layers to define the patterned breakable connection between the several layers of the build material support structure and the several layers of the patterned intermediate part. 
 
     
     
         10 . The method as defined in  claim 1  wherein the gas precursor is selected from the group consisting of a transition metal hydride, an alkaline earth carbonate that releases carbon dioxide when activated, and a solid state mixture of an oxidizable species and an oxidizing agent to produce an oxidation product in a gas state at a sintering temperature used during the heating. 
     
     
         11 . The method as defined in  claim 10  wherein one of:
 the gas precursor is the transition metal hydride, and the method further comprises exposing the intermediate structure to hydrogen gas during the heating; or 
 the gas precursor is the solid state mixture, and the method further comprises exposing the intermediate structure to an inert gas or a vacuum environment during the heating. 
 
     
     
         12 . A liquid functional agent for three-dimensional (3D) printing, comprising:
 a compound that is to be activated at a temperature within a sintering temperature range of a build material of an intermediate structure to generate gas pockets within a portion of the intermediate structure that is patterned with the liquid functional agent, the compound being selected from the group consisting of a transition metal hydride, an alkaline earth carbonate selected from the group consisting of barium carbonate and strontium carbonate, and a solid state mixture of an oxidizable species and an oxidizing agent to produce an oxidation product in a gas state in the sintering temperature range;   any of a surfactant or a dispersing aid;   a co-solvent; and   a balance of water.   
     
     
         13 . The liquid functional agent as defined in  claim 12  wherein:
 the compound is the transition metal hydride, and the transition metal hydride is titanium hydride; or 
 the compound is the solid state mixture and the oxidizable species includes carbon particles and the oxidizing agent is a transition metal oxide selected from the group consisting of Fe 2 O 3 , Mn 2 O 3 , Cr 2 O 3 , and Co 3 O 4 . 
 
     
     
         14 . The liquid functional agent as defined in  claim 12 , further comprising a binder. 
     
     
         15 . A three-dimensional (3D) printed article, comprising:
 a first object;   a second object; and   an irreversibly breakable connection between the first and second objects, wherein the irreversibly breakable connection comprises gas pockets.