Authors: Rainer Herrmann, Physicist, Dr.-Ing. Stefan Zaage
Foreign Body Detection in Cigarette Production by Microwave Measurement Technique
With this new measurement technique it is possible to detect contaminated rods in cigarette production. “Contaminated” means that the rod contains foreign bodies like plastic, rubber, wood, whole stems, metals, lumps of glue, residues of coal and additives of the tobacco process, independent of the colour of these foreign bodies. The detection is based on the application of microwaves, which are electromagnetic waves with a wavelength in the range of 10 cm. Because microwaves penetrate the paper of a cigarette easily, this method can be applied at the rod formation in a cigarette making machine, where no further contamination may occur.
The different interaction between microwaves and the tobacco rod in absence and presence of foreign bodies allows to apply a microwave sensor, which was designed for the online measurement of the rod density and moisture as a replacement of the conventional nucleonic sensors. During the last years this technique has proven it’s high precision and long-term stability for the on-line weight control. The signals of this microwave sensor can be used for the foreign body detection, because any foreign body in the rod which moves through the measuring zone, changes especially the moisture signal.