Novel measurement and monitoring system for forming processes based on piezoresistive thin film systems

The investigation of a novel sensor system, integrated in the main load region of forming machines, is the challenge. Therefore, it is important that the thin film system has an excellent tribological quality in combination with a piezoresistive behaviour. The layer system is deposited on the polished surface of a steel substrate. It has such geometries that it can be easily integrated in the drawing cushion of a deep drawing machine. The thin film sensor system exists out of a piezoresistive hydrogenated carbon layer. Onto this layer arrays of chromium structures are deposited. The structures are protected against wear by an insulating silicon doped hydrogenated carbon layer. The whole thin film system has a thickness of about 9 mu m. During the forming process the steel plate is in direct touch with the sensor system and moves over it. The position of the steel is measured in dependence on the forming stadium. The sensor system works as a control system to ensure that the shape of the product is perfect and without any cracks or creases.