Electromagnetic Forming,mechanical Electromagnetic Forming,Electromagnetic Forming
ELECTROMAGNETIC FORMING (EMF) is an assembly technique that is widely used to both join and shape metals
and other materials with precision and rapidity, and without the heat effects and tool marks associated with other
techniques. Also known as magnetic pulse forming, the EMF process uses the direct application of a pressure created in
an intense, transient magnetic field. Without mechanical contact, a metal workpiece is formed by the passage of a pulse of
electric current through a forming coil.
The parameters that determine the applicability of the EMF process are:
· Forming can be accomplished through a nonmetallic coating or container because the magnetic field passes
through electrical nonconductors
· Most of the forming takes place after the pressure impulse has ended, in contrast to most metal-forming
processes. The metal is rapidly accelerated, gaining a large amount of kinetic energy by moving only a short
distance during the impulse. This kinetic energy subsequently does the actual work of forming
· The metals that are most efficiently formed by EMF are those with relatively high electrical conductivity, such as
copper, aluminum, low-carbon steel, brass, and molybdenum. Metals with lower conductivity, such as stainless
steel, can be formed by using either very high energy or an intermediate, highly conductive "driver"
· The ratio of the masses of pieces used in assembly operations may be much more significant than their relative
mechanical strength or elastic properties. Because EMF does not use static forces, relatively light structures can
be used to support the dies
· No torque is applied to the workpiece in swaging and expanding operations, in contrast to spinning and rolling.
Because the magnetic field behaves much like a compressed gas, it exerts a uniform pressure that is relatively
independent of variations in spacing between the workpiece and the forming coil
· No lubricant is required because the contact between the magnetic field and the workpiece is frictionless
· The peak pressure is limited (by the strength of the forming-coil material) to much lower values than are commonly encountered in shearing, punching, and upsetting operations. However, the pressure that can be
applied by the magnetic pulse can be very high compared to the average pressure in mechanical forming
· The process, being purely electromagnetic, is not limited to repetition rate by the mechanical inertia of moving
parts. The timing of the magnetic impulse can be synchronized with microsecond precision, and machines can be
made to function at repetition rates of hundreds of operations per minute. The strength of the magnetic impulse
can be controlled electrically with high precision
The major application of EMF is the single-step assembly of metal parts to each other or to other components, although it
is also used to shape metal parts. Within the transportation industry, for example, one automotive producer assembles
aluminum driveshafts without welding to save a significant amount of weight in light trucks and vans to meet
requirements for reduced energy consumption. Using the EMF process allows the joining of an impact-extruded
aluminum yoke to a seamless tube without creating the heat-affected zone associated with welding. Numerous other uses
of the EMF process are described in the section "Applications" in this article.

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