Electromagnetic metal forming

An apparatus for deforming a sheet of material, said apparatus comprising:

• a die portion defining a profiled die surface;
• an electromagnetic actuator arranged opposite said profiled die surface;
• and
• a conductive frame configured to define a return path for eddy currents induced in a sheet of material secured in a position between said electromagnetic actuator and said profiled die surface upon activation of said electromagnetic actuator, wherein
• said eddy current return path and an electrical current path defined by said electromagnetic actuator define opposing current paths in said apparatus,
• said conductive frame and said die portion comprise respective sheet engaging portions configured to engage peripheral portions of said sheet of material in a position between said electromagnetic actuator and said profiled die surface, and
• said engagement of said peripheral portions of said sheet of material is such that a remaining portion of said sheet of material is substantially free to move in the direction of said profiled die surface in response to a repulsive electromagnetic force between said actuator and said sheet upon activation of said actuator.

An apparatus for deforming a sheet of material, said apparatus comprising a die portion, an electromagnetic actuator, and a conductive frame, wherein:

• said die portion defines a profiled surface;
• said electromagnetic actuator is arranged opposite said profiled surface of said die portion;
• said conductive frame is configured to
• secure said sheet of material in a position between said electromagnetic actuator and said profiled die surface,
• permit deformation of said sheet of material against said profiled die surface upon activation of said electromagnetic actuator, and
• define a return path for eddy currents induced in said sheet of material upon activation of said electromagnetic actuator such that said eddy current return path defines a circuit comprising at least a portion of said sheet of material and at least a portion of said conductive frame
• said sheet of material and said conductive frame are configured such that said eddy current return path and an electrical current path defined by said electromagnetic actuator define opposing current loops in a plurality of cross sections of said apparatus;
• said conductive frame and said die portion define sheet engaging portions configured to engage the substantially entire periphery of said sheet of material there between;
• said conductive frame and said die portion are configured to permit compression of said sheet of material between said respective sheet engaging portions of said conductive frame and said die portion;
• said apparatus further comprises a press configured to impart a compressive force upon said sheet of material secured in a position between said conductive frame and said die portion;
• and
• said compressive force exceeds said repulsive electromagnetic force by an amount sufficient to ensure substantially constant conditions of electrical contact between said sheet of material and said conductive frame as said electromagnetic actuator is cycled from an active to an inactive state.

A method of deforming a sheet of material utilizing an apparatus comprising a die portion, an electromagnetic actuator, and a conductive frame, wherein:

• said die portion defines a profiled surface, said electromagnetic actuator is arranged opposite said profiled surface of said die portion, and said conductive frame is configured to secure said sheet of material in electrical contact with said conductive frame in a position between said electromagnetic actuator and said profiled die surface, permit deformation of said sheet of material against said profiled die surface upon activation of said electromagnetic actuator, and define a return path for eddy currents induced in said sheet of material upon activation of said electromagnetic actuator;
• and
• said method comprises the steps of
• driving said actuator in an induction heating mode characterized by voltage and current profiles selected to heat said sheet of material through induction;
• and
• drive said actuator in an electromagnetic forming mode following said induction heating mode, wherein said electromagnetic heating mode is characterized by voltage and current profiles selected to generate a repulsive force between said actuator and said sheet of material of sufficient intensity to deform said sheet against said profiled die surface.