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 .