Methods related to inductive heating in extruders

A method for heating a feedstock of meltable or flowable material for additive manufacturing or 3D printing, comprising:

• a) providing a heating body of electrically conductive material, having inlet and outlet orifices connected via a passage or passages or mixing chamber to define a nozzle;
• b) said nozzle sandwiched between the two ends of, or inserted through a hole or gap in, a continuous or segmented core of material having high magnetic permeability but low electrical conductivity, forming a complete magnetic loop, said nozzle not oriented substantially in the same plane as said magnetic loop,
• c) one or more coils of electrically conductive wire passing through the center of said loop and around the outside of said loop, and one or more sources of alternating current connected to said coil or coils, inducing said magnetic flux lines and said eddy currents,
• d) feeding said feedstock in the form of filament, rod, wire, granules, or liquid stream into said inlet orifice or orifices;
• e) said feedstock being heated by contact with said nozzle, and
• f) extruding said feedstock from said outlet orifice or orifices.

A method for heating a feedstock of meltable or flowable material for adhesive application, comprising:

• a) providing a heating body of electrically conductive material, having inlet and outlet orifices connected via a passage or passages or mixing chamber to define a nozzle;
• b) said nozzle sandwiched between the two ends of, or inserted through a hole or gap in, a continuous or segmented core of material having high magnetic permeability but low electrical conductivity, forming a complete magnetic loop, said nozzle not oriented substantially in the same plane as said magnetic loop,
• c) one or more coils of electrically conductive wire passing through the center of said loop and around the outside of said loop, and one or more sources of alternating current connected to said coil or coils, inducing said magnetic flux lines and said eddy currents,
• d) feeding said feedstock in the form of filament, rod, wire, granules, or liquid stream into said inlet orifice or orifices;
• e) said feedstock being heated by contact with said nozzle, and
• f) extruding said feedstock from said outlet orifice or orifices.