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We depend on structural steel to keep us safe, in applications from building construction to automobile manufacturing. Over the years, we've found ways to make steel stronger and more durable. But it's easy to forget that the stronger the steel is, the harder it will be to shape, form, cut, and bend to build things with. Since steel is usually cut with steel tools, wear on the tools is substantial, requiring frequent maintenance, sharpening, and replacement.

Steel can also be cut with non-contact plasma tools or lasers, but these processes can be slow, inefficient, power-hungry, messy, or just plain dangerous for nearby workers. In any case, whether cut with energy or steel tools, the edges usually need to be ground or smoothed to remove burrs and rough or sharp edges resulting from the machining process.

Many of these problems can be overcome by a new process developed by a team lead by Verena Kräusel at the Fraunhofer Institute for Machine Tools and Forming Technology in Chemnitz, Germany. It's a non-contact energy-based process, but unlike plasma or laser technology, it's in the form of biologically safe magnetic fields. Following a similar principle to magnetic forming, magnetic punching may soon revolutionize steel manufacturing.

Magnetic Forming

Magnetic forming is a decades-old technique, but is used to squeeze or compress metals into shape. A popular demonstration, available on video-sharing sites such as YouTube, involves compressing a US quarter or other coin into a smaller, more dense, version of itself, the portrait of George Washington still intact (search for "shrinking quarter"). Lower-power versions can neatly crumple soda cans.

These techniques can be used on non-ferrous metals such as aluminum, even though they work by creating a very short, high-intensity magnetic pulse. A sufficiently strong magnetic field can affect many materials besides just iron. The magnetic field induces an electric current in the workpiece, which creates a magnetic field in the workpiece, and the action of these two fields working against each other results in the deformation.

These pulses are created by using a capacitor to push a very short-duration, high current through a coil of wire, resulting in a brief magnetic pulse over ten times more powerful than that produced by a medical MRI machine.

Magnetic Punching

The new twist in this process is that rather than simply metal forming, an even more powerful magnetic field is used to punch a hole. Unlike mechanical tooling, the hole is clean, there are no burrs or rough edges to smooth down, and since it is non-contact there is no dulling or mechanical tool wear which can cause inconsistent results over the tool's life. The magnetic punch is also faster and more efficient than laser cutting, taking just 0.2 seconds compared to a laser's 1.4 seconds and requiring a fraction of the electrical power to do so, without the associated vision hazard.

The current design can punch a hole up to 30mm (1.2 inches) in diameter in automobile structural steel 1mm (0.04 inches) thick using a force of 3500 atmospheres (26 tons per square inch).

It's a knockout (The Economist)
Electromagnetic Pulse Cuts Through Steel In 200 Milliseconds (Popsci)
Electromagnetic fields as cutting tools (Physorg)

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