A punch apparatus for punching hole patterns in thin sheet material. The apparatus includes a housing having a liquid-cooled cavity therein; a coil mounted in the liquid-cooled cavity; a driver disk made of a highly conductive material mounted in the liquid-cooled cavity, the driver disk mounted adjacent...http://www.google.es/patents/US4872381?utm_source=gb-gplus-sharePatente US4872381 - Programmable magnetic repulsion punching apparatus
Programmable magnetic repulsion punching apparatus
