Single screw micro-extruder for 3d printing

A single screw micro-extruder for a 3D printer having a printer head with a torque drive mechanism, the micro-extruder comprising:

• a feed chamber having a conically shaped feed surface converging downwardly, said feed chamber having an opening for receiving solid plastic pellets;
• an extrusion barrel having a length, a longitudinal axis extending downwardly from the feed chamber, and an inner conically shaped, concentric bore between input and output ends with a conical angle, the bore having a mouth at the input end and an exit opening at the output end with a melt section therebetween, and a diameter at the mouth being greater than a diameter of the exit opening;
• an extrusion nozzle at the output end of said extrusion barrel;
• and
• a rotatable screw having a length extending from the torque drive mechanism of the printer head and along the longitudinal axis through the conical bore of the extrusion barrel, the screw is rotatably supported by a bearing-seal housing and passes through the feed chamber, and further includes:
• i) a root core with a surface;
• ii) a flight located on and projecting radially from the root core, the flight having a lead length forming a channel with a helix angle and a helical path between the root core surface of the screw and an inner surface of the conically shaped, concentric bore of said extrusion barrel, the helical path extending from the input end and into the melt section of said extrusion barrel toward the extrusion nozzle;
• iii) an outermost surface of the flight having a land adjacent the inner surface of the conically shaped bore thereby forming a conical angle substantially equal to the conical angle of the barrel from the input end through the melt section of the extrusion barrel, such that the flight works closely with the inner surface of the bore to engage and wedgingly urge pellets from said input end downwardly through said extrusion barrel to the extrusion nozzle;
• iv) a constant or tapered diameter of the root core of the screw in a direction from the input end toward the output end of the extrusion barrel forms a decreasing channel root depth in the helical path for compression of the plastic pellets between the root core surface and the inner surface of the bore for pressurizing melt in the melt section of said extrusion barrel to exit the extrusion nozzle;
• and
• v) an auger section in the feed chamber to push plastic pellets toward the input end of the barrel.

A single screw micro-extruder for a 3D printer having a printer head with a torque drive mechanism, the micro-extruder comprising:

• a feed chamber having a conically shaped feed surface converging downwardly, said feed chamber having an opening for receiving solid plastic pellets;
• an extrusion barrel having a length not greater than 12 inches, a longitudinal axis extending downwardly from the feed chamber, and an inner conically shaped, concentric bore between input and output ends with a conical angle, the bore having a mouth at the input end and an exit opening at the output end with a melt section therebetween, and a diameter at the mouth being greater than a diameter of the exit opening and not greater than 2 inches;
• an extrusion nozzle at the output end of said extrusion barrel;
• and
• a rotatable screw having a length extending from the torque drive mechanism of the printer head and along the longitudinal axis through the conical bore of the extrusion barrel, the screw is rotatably supported by a bearing-seal housing and passes through the feed chamber, and further includes:
• i) a root core with a surface;
• ii) a flight located on and projecting radially from the root core, the flight having a lead length forming a channel with a helix angle and a helical path between the root core surface of the screw and an inner surface of the conically shaped, concentric bore of said extrusion barrel, the helical path extending from the input end and into the melt section of said extrusion barrel toward the extrusion nozzle;
• iii) an outermost surface of the flight having a land adjacent the inner surface of the conically shaped bore thereby forming a conical angle substantially equal to the conical angle of the barrel from the input end through the melt section of the extrusion barrel, such that the flight works closely with the inner surface of the bore to engage and wedgingly urge pellets from said input end downwardly through said extrusion barrel to the extrusion nozzle;
• iv) a constant or tapered diameter of the root core of the screw in a direction from the input end toward the output end of the extrusion barrel forms a decreasing channel root depth in the helical path for compression of the plastic pellets between the root core surface and the inner surface of the bore for pressurizing melt in the melt section of said extrusion barrel to exit the extrusion nozzle;
• and
• v) an auger portion in the feed chamber to keep plastic pellets moving toward the input end of the barrel.