A method of manufacturing a rotor assembly includes positioning a laminated stack of electric steel sheets with a plurality of conductor bars positioned within longitudinal grooves defined by the laminated stack in a mold, and casting an end ring in place over ends of the conductor bars. In order to cast the end ring in place, heated liquid aluminum is injected into a cavity defining the end ring, and circulated within the cavity and around the ends of the conductor bars to create relative movement between the liquid aluminum and the ends of the conductor bars to heat the conductor bars and flush oxides away from an outer surface of the conductor bars.