The need for minute processing is increasing recently, and electromagnetic piercing is again attracting attention. The electromagnetic piercing of metal foils theoretically does not need a punch and is performed using only a die. In this paper, we describe the piercing of both aluminum foil and stainless-steel foil using pressurization foil. The electromagnetic force generated in the aluminum foil is calculated with magnetic pressure and is proportional to the square of the diameter of the die hole. Therefore the piercing for a small hole of less than 1.0 mm diameter needs a high discharge energy. In experiments, the piercing of only a 15 μm-thick aluminum foil is impossible because the magnetic pressure is too low or the foil melts with softening, and the piercing of only a 50 μm-thick aluminum foil is also difficult. If a pressurization foil of 50 μm thick or 100 μm thick is added, a good piercing of these foils is enabled for holes from 0.5 to 2.5 mm diameter. The piercing of a 20 μm-thick stainless-steel foil is enabled by using a similar pressurization foil. However, a section of the pierced foil has both a sheared surface and a fractured surface.
