Importance

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Abstract

A method and apparatus for forming a metal object such as upsetting a fastener in a workpiece wherein first and second coils are provided in close proximity to and in electromagnetic association with each other, the first coil is in driving association with a forming tool adapted for forming the metal object and the first and second coils are supported in a manner allowing movement of the first coil relative to the second coil, and wherein an electric current pulse is supplied simultaneously to the first and second coils to produce a repulsive electromagnetic force sufficient to accelerate the first coil and driving the forming tool to form the metal object, the pulses being shaped in accordance with a characteristic of the metal object. The pulse shaping includes matching the magnetic force based on the current pulse with the stress-strain characteristic of the metal object being formed. In high energy impact fastener installation apparatus, there is balancing of the applied force from both ends of the fastener during simultaneous impact and upset to eliminate transfer of force to the workpiece and supporting structure. Advantages include a relatively less drastic fall off of mutual magnetic field with separation of the two coils, decreased heat load, increased output force, low reactive force to the supporting structure, increased efficiency and the ability to tailor the magnetic force to synchronize with the force requirements of the metal object during forming, and a gap-free joint containing the metal object.

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First Claim