Pulsed Power Technologies

Industrial use for contactless metal forming


Process description - EMF

Electromagnetic forming is a process using the energy density of a strong pulse shaping magnetic field for contactless forming of metals with high electrical conductivity. It belongs to the group of high speed forming processes, whereas the workpiece material will be deformed with strain rates between 1,000 and several 10,000 per second.

The sudden discharge of a capacitor battery through a tool coil, e.g. a cylindrical coil, causes a fast increasing magnetic field within the coil. The pulse shaping coil current can be of several 100 kA within a period of microseconds. The magnetic field is accordingly strong and short.

If a tubular workpiece with good electrical conductivity is located within the tool coil, a high current in contrary direction will be induced in the workpiece wall. For a limited time, this induced current prevents the magnetic field from penetrating through the workpiece wall. Thus, the strong magnetic field will be bounded by the small gap between tool coil and workpiece.

The energy density of a magnetic field is equivalent to an acting pressure:

which now acts in radial direction on both the workpiece and the tool coil. A plastic deformation begins, if the occurring stress exceeds the yield strength of the material.


The kind of loading is determined by the arrangement of tool coil and workpiece:

A workpiece located within the tool coil will be compressed, while, conversely, with a coil located within a tubular workpiece, an expansion of the tube will be caused. A third process variant is the forming operation of sheet metals by means of a flat coil.