Ultrasonic technologies are not only quick and efficient but also extremely eco-friendly for processing thermoplastics, films and fabrics. The principle of the technology is based on the generation of internal heat (molecular friction) by ultrasound and the boundary friction in the join or separation zones of thermoplastics.
Ultrasound is mechanical oscillation at a frequency of approx. 16 kHz to 1 GHz. Sound of less than 20 kHz is perceptible by humans and is therefore described as audible sound. Frequencies of more than 500 kHz are hyper-sound.
Ultrasound in the lower frequency range of 20 kHz to 100 kHz has industrial applications for plastics processing. The ultrasonic systems of SONOTRONIC operate at 20 kHz 30 kHz or 35 kHz. The ultrasound frequency is produced by a generator. The generator converts mains voltage into high-frequency high voltage and transfers this to the welding stack, which is made up of the converter, the booster (amplitude transformation unit) and the sonotrode (welding tool). The converter converts the incoming voltage by electrostriction into mechanical oscillations of the same frequency and conducts them via the booster and sonotrode to the workpiece. Oscillation absorption, accompanied by the application of pressure and the vertical introduction of mechanical oscillations, creates interface and molecular friction in the joining or separation zone.
The result is local heating of the workpiece material in the join zone. This plasticising process makes it possible for one or more workpieces to be welded, cut, punched, riveted or embossed, either continuously or in cycles . When processing textiles, fabrics can be washed by using ultrasound thermofixed by local heating. In addition, ultrasound offers a further application in environmental technology in the sonication of bio-solids: instead of local heating, ultrasound creates intensive cavitation bubbles. The implosion of the cavitation bubbles upsets the liquid so that, for example, the biological mass is better converted or disinfected.