http://205.243.100.155/frames/shrinker.html
Theory of Operation:
The Quarter Shrinker uses a technique called high velocity electromagnetic forming, or "Magneforming". This is a "high energy rate" process that was originally developed by the aerospace industry in conjunction with NASA, and has been popularized by Aerovox, Grumman, and Maxwell. It involves quickly discharging a high energy capacitor bank through a work coil to generate a very powerful, rapidly changing magnetic field which then "forms" the metal to be fabricated. The technique uses pulsed power to generate an extremely high current pulse over a very short interval. Although electromagnetic forming works best with metals that have relatively high electrical conductivity (such as copper, silver, or aluminum), it will also work to a limited extent with poorer conducting metals or alloys such as steel or nickel.