Methods for fiber reinforced additive manufacturing

Abstract

Various embodiments related to three dimensional printers, and reinforced filaments, and their methods of use are described. In one embodiment, a void free reinforced filament is fed into an extrusion nozzle. The reinforced filament includes a core, which may be continuous or semi-continuous, and a matrix material surrounding the core. The reinforced filament is heated to a temperature greater than a melting temperature of the matrix material and less than a melting temperature of the core prior to extruding the filament from the extrusion nozzle.

1 .- 20 . (canceled) 
     
     
         21 . A method for additive manufacturing, the method comprising steps of:
 threading an end of a filament through a channel of a printhead to an outlet, the filament comprising a substantially continuous fiber core extending within a matrix material, and threading including feeding the filament in an unmelted state;   maintaining a stiffness of the filament, including passing the filament through a cold feed zone having a temperature that is below the melting temperature of matrix material; and   heating the filament at a temperature greater than a melting temperature of the matrix material in a transverse pressure zone at the outlet.   
     
     
         22 . The method of  claim 21 , wherein the temperature of the cold feed zone is below the glass transition temperature of the matrix. 
     
     
         23 . The method of  claim 21 , wherein the substantially continuous fiber comprises a sectioned continuous core. 
     
     
         24 . The method of  claim 21 , wherein the step of maintaining a stiffness comprises preventing wall contact of the filament until it has been threaded to the outlet of the printhead. 
     
     
         25 . The method of  claim 21 , wherein feeding comprises pushing the filament in an unmelted state. 
     
     
         26 . The method of  claim 25 , wherein when pushed the unmelted filament is sufficiently stiff to prevent buckling. 
     
     
         27 . The method of  claim 25 , wherein when pushed the unmelted filament is sufficiently stiff to prevent peeling off. 
     
     
         28 . The method of  claim 25 , wherein when pushed the unmelted filament is sufficiently stiff to prevent curling. 
     
     
         29 . The method of  claim 21 , wherein the matrix material is characterized in that it exhibits no appreciable tack in ambient conditions. 
     
     
         30 . The method of  claim 21 , wherein prior to the step of threading is a step of cutting the filament. 
     
     
         31 . The method of  claim 21 , wherein prior to the step of threading is a step of running out the filament. 
     
     
         32 . The method of  claim 21 , wherein prior to the step of threading is a step of separating the filament. 
     
     
         33 . The method of  claim 21 , wherein the step of maintaining further comprises feeding the filament through a heated zone having a cavity that is larger than that of the cold feed zone. 
     
     
         34 . The method of  claim 33 , wherein the cavity of the heated zone has a larger diameter than that of the cold feed zone. 
     
     
         35 . The method of  claim 33 , wherein the heated zone diverges to a lip at the outlet. 
     
     
         36 . The method of  claim 21 , further comprising a step of pre-heating the filament through a hot melt zone between the cold feed zone and the transverse pressure zone. 
     
     
         37 . The method of  claim 21 , wherein the step of heating the filament at a temperature greater than the melting temperature of the matrix material in the transverse pressure zone melts the matrix material interstitially within one or more fibers within the filament. 
     
     
         38 . The method of  claim 21 , further comprising a step of applying an ironing force to the filament with a lip. 
     
     
         39 . The method of  claim 21 , further comprising a step of applying a translating force to the filament with the lip. 
     
     
         40 . The method of  claim 39 , wherein the translating force comprises a tension on a part and/or a surface. 
     
     
         41 . The method of  claim 21 , wherein the transverse pressure zone is a print head tip. 
     
     
         42 . The method of  claim 21 , wherein the transverse pressure zone is an ironing lip.