Eliminating Faults During Production Of Metal Sheets

Fuel is expensive, so cars need to become lighter and lighter. To ensure that this weight loss does not come at the expense of safety, the vehicles’ metal sheets are not only getting thinner but also harder – ultra-hard. This means that the production process, too, has to be re-adapted. “Several process steps are needed to manufacture car body components,” explains Dipl.-Ing. Sören Scheffler of the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz. “If you look at a car, you can see that each of its sheet metal parts is extremely large.

And the cost of this material is steadily increasing. If the process used to draw, cut, perforate and calibrate the sheets is not set correctly, the resulting components will not meet the specified quality standards and have to be thrown away. In order to limit the number of rejects and keep costs down, today’s car manufacturers are seeking ways of making their processes more reliable.” The experts at the IWU have developed a special system for monitoring deep-drawing and forming processes, enabling production to be constantly and consistently supervised.

The system uses sensors to monitor drawing-in during production. The collected data are then transmitted online to a computer. “The art lies in recognizing from these data whether there are any process fluctuations that need balancing out. We do this by comparing the values recorded online with previously specified target data,” explains Scheffler. If the researchers discover any deviations, they can intervene even during the deep-drawing or forming process with the aid of elastic tools and tool-integrated piezo-elements, for example, and thus make the necessary readjustments. “As we are able to detect process fluctuations at an early stage, we can significantly reduce the reject rate. What’s more, we can recognize faulty parts and separate them out immediately,” says the expert, highlighting the system’s advantages. “This fully automatic process supervision perfectly complements the subsequent manual quality inspection.”

The new Fraunhofer technique is already in use as a prototype. It is suitable for all processes involving the handling of metal sheets, so it could also be used in the manufacture of consumer goods such as sinks, for instance. .

They will be presenting the new technique at the joint Fraunhofer stand, G34, in Hall 11 at the Euroblech trade fair in Hanover from October 21 to 25, 2008.