Abstract: Methods related to inductive heating in extruders. In some embodiments, a method for heating a feedstock or liquid material can include providing a heating body having inlet and outlet orifices connected via a passage or passages or mixing chamber to define a nozzle, and forming a magnetic loop with a coil of conductive wire wound through the center and around the outside of a core of magnetic but electrically non-conductive or low-conductivity material. The method can further include a high-frequency alternating current applied to the coil, producing a magnetic flux locally heating the nozzle. Some embodiments have passive regulation or limiting of nozzle temperature by selection of a core material with an appropriate Curie temperature.

Abstract: One embodiment of a heated nozzle for extruding meltable material consists of an electrically conductive nozzle, comprised of an inlet, an outlet, and a passage connecting inlet and outlet. The nozzle fits into a hole or gap cut or formed through a loop of high permeability soft magnetic material such as ferrite or pressed iron powder. Electrically conductive wire is coiled around and through this magnetic loop to form a coil. A high-frequency alternating current is supplied to the coil, inducing a magnetic field in the magnetic core. The magnetic field, when passing through the electrically conductive nozzle, induces eddy currents that heat the nozzle to melt the material entering the inlet.