With the help of the MULTICELL concept, small multi-head applications can be easily implemented. In general, the plastic parts to be welded are loaded directly below the sonotrodes. A shuttle table can be optionally integrated for improved handling. This modular concept is particularly suitable for 20 kHz applications with sound insulation and can be customized by installation of a large number of accessory options. The compact make-up and high degree of mobility allow for universal application in manufacturing.