Abstract: A system for processing plastic feed material includes a machine having a barrel and a screw that rotates in a repetitive cycle in the barrel. An induction winding encircles and extends along an outer surface of the barrel. A control system includes a controller that determines a duty cycle referenced to a length of the machine cycle in response to an error between a desired barrel temperature and a current barrel temperature. The controller electrically connects the power supply to the induction winding at least once during each cycle for a period whose length corresponds to the duty cycle.

Abstract: A system for processing plastic feed material includes a machine having a barrel and a screw that rotates in a repetitive cycle in the barrel. An induction winding encircles and extends along an outer surface of the barrel. A control system includes a controller that determines a duty cycle referenced to a length of the machine cycle in response to an error between a desired barrel temperature and a current barrel temperature. The controller electrically connects the power supply to the induction winding at least once during each cycle for a period whose length corresponds to the duty cycle.

Abstract: A system for processing plastic feed material includes a barrel having an upstream feed section and a downstream output section. A screw, supported for rotation in the barrel, cooperates with an inner surface of the barrel to form a path in which the feed material moves toward the output section. A heating system includes an induction winding encircling and extending along a portion of an outer surface of the barrel, and a gap interposed between the induction winding and the barrel and having a nonuniform thickness that varies around the periphery and corresponds to a varying wall thickness of the barrel.

Abstract: A system for supplying processed material includes a barrel for transporting the processed material, having a chamber and an electrically conductive wall enclosing the chamber. The barrel has a length and an outer surface. Thermal insulation extends along at least a portion of the length and around the outer surface and provides an exterior surface whose contour is uniform and formed without grooves. A coil comprising an electric conductor is encased in an electrical insulating sheath. The coil contacts and encircles the exterior surface in loops forming an induction winding that extends along at least a portion of the length and around the exterior surface in a spiral path. An induction power supply is used for supplying alternating current to the coil at a relatively high frequency.

Abstract: Disclosed herein is an apparatus and method with inductive heating of an electrically conductive workpiece such as a barrel used in molding or extrusion, having a layer of thermal insulation interposed between the induction windings and the workpiece, and using alternating current (AC) at an elevated frequency. Further, variable pitch induction windings may be used to generate a non-uniform and calculated heat input profile, such as to compliment the configuration of a screw for transporting material through the barrel.