48.5 MAGNETIC PULSE FORMING

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Basic operation,

1. A large current discharge is directed through a coil. The coil has been placed inside another shape.

2. The discharging current creates a magnetic field. In the nearby sheet of metal an opposing magnetic field is induced. The result is that the two magnetic fields oppose and a force moves the sheet away from the coil.

3. Over a period of time the part is deformed, often to the shape of a mandrel, or other form.

Applications,

- fittings for ends of tubes

- embossing

- forming

Capacitor banks are used to accumulate charge for larger discharges.

The part is formed to a mandrel that has a negative image of the part.

The method generates pressures up to 50 Kpsi creating velocities up to 900 fps, production rates can climb to 3 parts a second.

Applications,

- ball joint seals

- fuel pumps

- baseball bats

Generally there are three methods of magnetic forming,

- swaging

- expanding

- embossing and blanking

Swaging - An external coil forces a metal tube down onto a base shape (tubular coil).

Expanding - an inner tube is expanded outwards to take the shape of an outer collar (tubular coil).

Embossing and Blanking - A part is forced into a mold or over another part (a flat coil) - This could be used to apply thin metal sheets to plastic parts.

Advantages,

- easy to control

- allows forming of metals to any material

- no contact eliminates many requirements such as lubricants, heat dissipation, surface repair, etc.

- parts are uniform

- no tool wear

- minimal operator skill

- very strong joints

- energy efficient

- easy installation

- high production rates (typically a few seconds)

Disadvantages,

- complex shapes not possible

- no pressure variations over work

- limits forming pressures