Build material switching

Abstract

A three-dimensional printer uses transitional lengths of build material to facilitate changes from one material to another during a fabrication process. The transitional lengths of build material may be positioned inside a fabricated object, such as for infill, or outside the fabricated object where undesirable aesthetic properties of the transitional lengths will not impact the desired distribution of different build materials on the surface of the fabricated object.

What is claimed is: 
     
         1 . A method for three-dimension fabrication, the method comprising:
 receiving a tool path for an extruder to fabricate an object from a three-dimensional model, the three-dimensional model including a surface featuring at least a first build material and a second build material, wherein the first build material and the second build material have at least one different material property relative to one another, and the tool path defining interstitial void space between infill formed by the tool path for use in fabricating the object;   identifying, within the tool path, a change from the first build material to the second build material along the surface;   calculating a transition having a transitional length including a beginning and an end for the change from the first build material to the second build material to occur, the calculation of the transition incorporating a safety margin to ensure that the transition is completed over the transitional length;   altering the tool path to cause a continuous excursion from the surface of the object for the transition having the transitional length including the safety margin, the transitional length beginning after the continuous excursion from the surface of the object and completing before a return to the surface of the object, wherein the continuous excursion includes a length located within the interstitial void space between infill formed by the tool path;   changing build material supplied to the extruder from the first build material to the second build material; and   fabricating a portion of the object by moving the extruder along the continuous excursion after changing the build material supplied to the extruder.   
     
     
         2 . The method of  claim 1 , wherein the at least one different material property between the first build material and the second build material includes an optical property. 
     
     
         3 . The method of  claim 2 , wherein the optical property includes one or more of an opacity, a color, and a finish. 
     
     
         4 . The method of  claim 1 , wherein the at least one different material property between the first build material and the second build material includes a mechanical property. 
     
     
         5 . The method of  claim 4 , wherein the mechanical property includes one or more of an elasticity, a strength, and a melting point. 
     
     
         6 . The method of  claim 1 , wherein the at least one different material property between the first build material and the second build material includes a chemical property. 
     
     
         7 . The method of  claim 1 , wherein the at least one different material property between the first build material and the second build material includes a thermal property. 
     
     
         8 . The method of  claim 1 , wherein the at least one different material property between the first build material and the second build material includes an electrical property. 
     
     
         9 . The method of  claim 1 , wherein changing build material includes splicing a first length of filament formed of the first build material to a second length of filament formed of the second build material. 
     
     
         10 . The method of  claim 1 , wherein changing the build material includes changing from the first build material to the second build material at a feed of the extruder during a build. 
     
     
         11 . The method of  claim 1 , wherein the transitional length is sufficiently great for a complete change at the extruder from the first build material to the second build material. 
     
     
         12 . A method for three-dimension fabrication, the method comprising:
 receiving a tool path for an extruder to fabricate an object from a three-dimensional model, the three-dimensional model including at least a first build material and a second build material, wherein the first build material and the second build material have at least one different material property relative to one another, and the tool path defining interstitial void space between infill formed by the tool path for use in fabricating the object;   identifying, within the tool path, a change from the first build material to the second build material;   calculating a transitional length for completing the change from the first build material to the second build material;   altering the tool path to include a continuous excursion from a surface of the object, the continuous excursion including a length at least as great as the transitional length before returning to the surface, and at least a portion of the length located within the interstitial void space between infill formed by the tool path;   changing build material supplied to the extruder from the first build material to the second build material; and   fabricating a portion of the object by moving the extruder along the continuous excursion after changing the build material supplied to the extruder.   
     
     
         13 . The method of  claim 12 , wherein the at least one different material property between the first build material and the second build material includes an optical property. 
     
     
         14 . The method of  claim 13 , wherein the optical property includes one or more of an opacity, a color, and a finish. 
     
     
         15 . The method of  claim 12 , wherein the at least one different material property between the first build material and the second build material includes a mechanical property. 
     
     
         16 . The method of  claim 15 , wherein the mechanical property includes one or more of an elasticity, a strength, and a melting point. 
     
     
         17 . The method of  claim 12 , wherein the at least one different material property between the first build material and the second build material includes a chemical property. 
     
     
         18 . The method of  claim 12 , wherein the at least one different material property between the first build material and the second build material includes a thermal property. 
     
     
         19 . The method of  claim 12 , wherein the at least one different material property between the first build material and the second build material includes an electrical property. 
     
     
         20 . The method of  claim 12 , wherein the transitional length is sufficiently great for a complete change at the extruder from the first build material to the second build material.