System and method for 3d printing with metal filament materials

Abstract

An additive manufacturing system configured to a 3D print using a metal wire material includes a drive mechanism configured to feed the metal feedstock into an inlet tube and a liquefier. The liquefier has a chamber configured to accept the metal feedstock from the inlet tube. The metal feed stock is heated in the chamber such that a melt pool is formed in the chamber. The liquefier has an extrusion tube in fluid communication with the chamber, the extrusion tube having a length (L) and a diameter (D) wherein the ratio of length to diameter (L/D) ranges from about 4:1 to about 20:1. The system has a platen with a surface configured to accept melted material from the liquefier, wherein the platen and the liquefier move in at least three dimensions relative to each other. The system includes a regulated source of pressurized inert gas flowably coupled to the liquefier and configured to place a controlled positive pressure onto the melt pool sufficient to overcome the resistance of the extrusion tube such that a part may be formed by the extrusion of the liquidus metal along toolpaths defined by the relative motion of the liquefier and the platen.

1 - 20 . (canceled) 
     
     
         21 . An additive manufacturing system configured to 3D print a part from a metal material, the system comprising:
 an inlet tube for conveying a metal feedstock in wire form;   a liquefier comprising:
 a chamber configured to accept the metal feedstock from the inlet tube at an upstream end thereof and to accumulate melted metal feedstock as a melt pool in a downstream end thereof; 
 an extrusion tube in fluid communication with the chamber, the extrusion tube having a length (L) and a diameter (D) and terminating in an extrusion tip, wherein the ratio of length to diameter (L/D) ranges from about 4:1 to about 20:1, and wherein the L/D ratio is selected to resist a flow of liquidus metal from the melt pool through the extrusion tube at atmospheric pressure; and 
 a heater configured to impart heat into the chamber and the extrusion tube, and wherein the heat causes the metal feedstock in the chamber to melt and form the melt pool; 
   a drive mechanism configured to feed the metal feedstock through the inlet tube and into the liquefier at a controlled rate;   a platen having a surface configured to accept melted material from the liquefier, wherein the platen and the liquefier move in at least three dimensions relative to each other; and   a regulated source of pressurized inert gas flowably coupled to the liquefier and configured to place a controlled positive pressure onto the melt pool sufficient to overcome the resistance of the extrusion tube such that liquidus metal will flow from chamber through the extrusion tip and onto the platen in a continuous extrusion stream such that a part may be formed by the extrusion of the liquidus metal along toolpaths defined by the relative motion of the liquefier and the platen and without use of further flow control mechanisms.   
     
     
         22 . The additive manufacturing system of  claim 21 , wherein the inlet tube is a ceramic tube. 
     
     
         23 . The additive manufacturing system of  claim 21  and further comprising a cooling unit at least partially positioned about the inlet tube, wherein the cooling unit is configured to remove heat from the metal feedstock before it enters the liquefier. 
     
     
         24 . The additive manufacturing system of  claim 21 , and further comprising a source of cryogenic gas wherein the cryogenic gas directly contacts the metal wire feedstock upstream of the liquefier. 
     
     
         25 . The additive manufacturing system of  claim 23 , wherein the cooling unit comprises a jacket with an internal chamber with an inlet and an outlet such that a cooling fluid can flow through the jacket. 
     
     
         26 . The additive manufacturing system of  claim 21 , wherein L/D ranges from about 4:1 to 10:1 
     
     
         27 . The additive manufacturing system of  claim 21 , wherein the extrusion tip is replaceable. 
     
     
         28 . The additive manufacturing system of  claim 21 , wherein the liquefier further comprises a purge port in fluid communication with the chamber, wherein the purge port is configured to be opened to remove slag buildup and closed during extrusion. 
     
     
         29 . The additive manufacturing system of  claim 21  and further comprising:
 a first electrode attached to the liquefier; 
 a second electrode attach to the platen; and 
 an electric source connected to both the first and second electrode wherein the electric source is directed through either the first or second electrode and passed to the other electrode through the liquidus metal between the first and second electrodes wherein a change in voltage changes a viscosity of the extruded metal. 
 
     
     
         30 . The additive manufacturing system of  claim 21 , wherein D ranges from about 0.012 inches to about 0.020 inches and L ranges from about 0.048 inches to about 0.4 inches. 
     
     
         31 . The additive manufacturing system of  claim 21 , wherein the controlled positive pressure ranges from about 2-20 psig. 
     
     
         32 . The additive manufacturing system of  claim 21 , wherein the controlled positive pressure ranges from about 5-15 psig.