A revolutionary new process to punch holes in steel without leaving burrs and at lower cost than heavy presses is being developed by a group in Germany according to an article in the Economist magazine. The paper reported this week how Verena KrÃƒÂ¤usel and her colleagues at the Fraunhofer Institute for Machine Tools and Forming Technology in Chemnitz, Germany have found a way to use an EMP device to shape and punch holes through steel. This could transform manufacturing by doing away with the need to use large, heavy presses to make goods ranging from cars to washing machines. OK what’s an EMP device I hear you say, sounds like something developed for a doomsday battlefield scenario? Well you would be right in as much as one notorious effect of Electro Magnetic Pulses is to disable an enemy’s computers, electronic control systems and telecommunications by delivering a blast of electromagnetic energy from an atomic bomb detonated at high altitude. But there is also a peaceful application where EMP devices are used in industry to shape soft metals like aluminum and copper.
The Fraunhofer Institute has taken this concept and raised it to another level by enhancing an existing electromagnetic forming machine. The article explains that such machines use a bank of capacitors to discharge a current rapidly through a coil. The coil converts the current into a powerful magnetic field. When the component to be worked is placed next to such a machine, the coil induces in it a corresponding field. Like poles repel, and the repulsion between the two fields is strong enough to make the metal distort. By strengthening the coil and speeding up the rate of discharge, Frau KrÃƒÂ¤usel and her team have increased the power of the machine so that it can punch through steel. The enhanced machine has an impact pressure of 3,500 atmospheres (51,450 lbs/sq in) enough to punch 1-2 diameter holes through the kind of steel used in the automotive industry for car bodies, around 0.040 thick. Tests by the institute have shown it works equally well on hardened and stainless steels.
The work is being sponsored by German industry heavyweights like Volkswagen who see the technique as having distinct advantages over the traditional heavy press route. Presses leave burrs when they punch through metals that have to undergo a subsequent dressing process. In addition, press dies are expensive and wear out requiring replacement. Lasers are an alternative to presses but take time to cut a hole, typically 1.4 seconds against the EMP device at 0.2 second. An EMP device leaves no burr, there is no die to wear out and although different size holes require different size coils once they are made, the coil never wears out. A blending of the technology’s ability to mold metals into forms and this new ability to punch shapes or holes opens the possibility of a CNC EMP machine that could both form and punch in combined operations reducing time and life cycle costs for manufacturers of metal components.