Researchers use EMPT to cut steel

Researchers in Germany have developed a new method for making holes in press-hardened steel bodywork using electromagnetic pulse technology (EMPT).

It is claimed the technology, which was previously used primarily to expand or neck aluminium tubes, is faster and creates less burr than other methods.

The development included support from engineers at Volkswagen and the Fraunhofer Institute for Machine Tools and Forming Technology (IWU) in Chemnitz.

Verena Kräusel, head of department at the IWU, explained a laser cutter takes around 1.4 seconds to cut a hole, whereas the EMPT can do the job in approximately 200 milliseconds. She said: ‘Our method is up to seven times faster.’

The team claims another advantage is that it produces no burr — unwanted material that occurs on the other side of steel when it is pierced. Therefore, the EMPT technique does away with the need for a finishing process.

Also, the process does not wear out cutting tools, meaning there is no cost for replacement.

The pulse generators comprise a coil, a capacitor battery, a charging device and high-current switches.

When the switch closes, the capacitors discharge via the coil, producing a high-pulsed current. The coil converts the energy stored in the capacitors into magnetic energy.

To be able to use this process to cut steel, the researchers had to modify the coil to ensure the resulting electromagnetic field is strong enough. The pressure of the field that hits the steel must be so high that it forcibly expels the material from the sheet.

Kräusel said: ‘The impact pressure on the steel is approximately 3,500 bar, which equates to the weight of three small cars on a single fingernail.’

PSTproducts in Alzenau provided the original EMPT system. The researchers are now developing the coils for various cutting geometries to meet customer demands.