Three-dimensional fabrication with locally activated binding of sinterable powders

Abstract

A powder bed is filled layer by layer with a powdered build material containing an activatable binder. The binder in each new layer is locally activated according to a computerized three-dimensional model of an object to fabricate, layer by layer, a sinterable net shape of the object within the powder bed. 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 powdered build material in a powder bed, the powdered build material including a sinterable powder of a material selected for sintering into a final part and an activatable binder for selectively adhering the sinterable powder in a shape;   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 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 powdered build material includes a ceramic powder. 
     
     
         5 . The method of  claim 1  wherein the powdered build material includes a metallic powder. 
     
     
         6 . The method of  claim 1  wherein the powdered build material is loaded with at least fifty percent sinterable powder by volume. 
     
     
         7 . The method of  claim 1  wherein locally activating the activatable binder includes thermally activating the activatable binder. 
     
     
         8 . The method of  claim 7  wherein locally activating the activatable binder includes locally activating the activatable binder with a thermal print head. 
     
     
         9 . The method of  claim 7  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. 
     
     
         10 . The method of  claim 1  wherein locally activating the activatable binder includes activating the activatable binder with a local application of microwave energy. 
     
     
         11 . The method of  claim 1  wherein locally activating the activatable binder includes applying a solvent to the activatable binder to reflow the activatable binder to adjacent particles of the sinterable powder. 
     
     
         12 . The method of  claim 1  wherein the activatable binder include a liquid binder. 
     
     
         13 . The method of  claim 12  wherein the liquid 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. 
     
     
         14 . The method of  claim 1  wherein the activatable binder includes at least one of polypropylene, polyethylene, nylon, and acrylic. 
     
     
         15 . 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. 
     
     
         16 . The method of  claim 15  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. 
     
     
         17 . A system for additive fabrication of a sinterable object, the system comprising:
 a powder bed;   a supply of a powdered build material for the powder bed, the powdered build material including a sinterable powder of a material selected for sintering into a final part and an activatable binder for selectively adhering the sinterable powder in a shape;   a spreader for spreading the powdered build material in a layer across the powder bed; and   a tool configured to locally activate 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.   
     
     
         18 . The system of  claim 17  wherein the spreader is a bi-directional spreader. 
     
     
         19 . The system of  claim 17  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. 
     
     
         20 . The system of  claim 17  wherein the powdered build material includes at least one of a ceramic powder or a metallic powder. 
     
     
         21 . The system of  claim 17  wherein the activatable binder includes at least one of polypropylene, polyethylene, nylon, and acrylic. 
     
     
         22 . The system of  claim 17  wherein the tool includes a thermal print head positionable to locally activate the activatable binder according to the two-dimensional cross-section. 
     
     
         23 . The system of  claim 17  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. 
     
     
         24 . The system of  claim 17  wherein the tool includes an inkjetting print head configured to locally activate the activatable binder by locally applying a solvent selected to reflow the activatable binder to adjacent particles of the sinterable powder.