Three-dimensional fabrication with locally activated binding of sinterable powders

Abstract

A powder bed is filled layer by layer with a sinterable powder and a liquid binder. After the liquid binder is applied, the liquid binder can be activated, e.g., by selectively curing cross-sections of the binder according to a computerized three-dimensional model of an object. In this manner, a sinterable net shape object can be formed within the powder bed layer by layer. The sinterable net shape can then be removed, debound as appropriate, and sintered into a final part.

What is claimed is: 
     
         1 . A method comprising:
 depositing a layer of a sinterable powder in a powder bed, the sinterable powder including a material selected for sintering into a final part;   applying an activatable binder to the layer;   locally activating the activatable binder in the layer according to a two-dimensional cross-section of a computerized three-dimensional model of an object, thereby binding the sinterable powder within the layer with an activated binder according to the two-dimensional cross-section; and   repeating the steps of depositing, applying and locally activating for each of a plurality of sequential layers within the powder bed to form a sinterable net shape of the object from the sinterable powder and the activated binder.   
     
     
         2 . The method of  claim 1  further comprising removing the sinterable net shape of the object from the powder bed and debinding the sinterable net shape of the object. 
     
     
         3 . The method of  claim 1  further comprising sintering the sinterable net shape of the object into the final part. 
     
     
         4 . The method of  claim 1  wherein the sinterable powder includes a ceramic powder. 
     
     
         5 . The method of  claim 1  wherein the sinterable powder includes a metallic powder. 
     
     
         6 . The method of  claim 1  wherein locally activating the activatable binder includes thermally activating the activatable binder. 
     
     
         7 . The method of  claim 6  wherein locally activating the activatable binder includes locally activating the activatable binder with a thermal print head. 
     
     
         8 . The method of  claim 6  wherein locally activating the activatable binder includes locally activating the activatable binder using one or more of an infrared heat source, an infrared heating mask, and a laser. 
     
     
         9 . The method of  claim 1  wherein locally activating the activatable binder includes activating the activatable binder with a local application of microwave energy. 
     
     
         10 . The method of  claim 1  wherein the activatable binder includes a liquid that cures upon exposure to one or more types of light, and further wherein locally activating the activatable binder includes selectively exposing the layer to the one or more types of light according to the two-dimensional cross-section. 
     
     
         11 . The method of  claim 1  further comprising fabricating a support structure below a surface of the sinterable net shape of the object within the powder bed. 
     
     
         12 . The method of  claim 11  further comprising fabricating an interface layer between the support structure and the surface of the sinterable net shape of the object, the interface layer structurally configured to resist bonding to the sinterable net shape of the object during sintering. 
     
     
         13 . A system for additive fabrication of a sinterable object, the system comprising:
 a powder bed;   a supply of a sinterable powder for the powder bed, the sinterable powder including a material selected for sintering into a final part;   a spreader for spreading the sinterable powder in a layer across the powder bed;   an applicator for applying an activatable binder to the layer; and   a tool configured to locally activate the activatable binder in the layer in a shape according to a two-dimensional cross-section of a computerized three-dimensional model of an object, thereby binding the sinterable powder within the layer with an activated binder according to the two-dimensional cross-section.   
     
     
         14 . The system of  claim 13  wherein the spreader is a bi-directional spreader. 
     
     
         15 . The system of  claim 13  further comprising a deposition tool configured to apply an interface material at an interface adjacent to the shape in the layer, wherein the interface material resists bonding of a surface of the shape to adjacent sinterable powder during sintering. 
     
     
         16 . The system of  claim 13  wherein the sinterable powder includes at least one of a ceramic powder or a metallic powder. 
     
     
         17 . The system of  claim 13  wherein the activatable binder includes at least one of polypropylene, polyethylene, nylon, and acrylic. 
     
     
         18 . The system of  claim 13  wherein the tool includes a thermal print head positionable to locally activate the activatable binder according to the two-dimensional cross-section. 
     
     
         19 . The system of  claim 13  wherein the tool includes at least one of an infrared heat source, an infrared heating mask, and a laser configured to locally activate the activatable binder according to the two-dimensional cross-section. 
     
     
         20 . The system of  claim 13  wherein the tool includes a light source configured to locally activate the activatable binder according to the two-dimensional cross-section.