The secret of ultrasonic welding is focusing the ultrasound with an energy director. In this way, it is possible to generate heat and subsequently melt, restricted to a locally defined area, while using only little energy. Large-area contact surfaces are counterproductive; they require high power and only achieve undefined joining areas with poor strength.
Energy focusing is achieved by:
- the energy director (ED)
- sonotrode design
- contouring of the anvil profile
Focusing by the sonotrode shape (weld tool); e.g. during the ultrasonic staking process, the sonotrode assumes the task of energy concentration.
The centering tip serves as melting initiation aid.
