Ultrasonic-welding-technique with a rotating sonotrode


The requirements:


The welding (in terms of boning) of several textiles- or natural-fiber-layers requires the fabrics to consist to a certain amount of thermoplastic material which is deformable by heat.
Most of today's conventionally used technical-textiles are perfectly suited for joining via welding technique, as they are based on synthetic-basic-materials.


The components:

The proceedings in the detail

In order to bond materials via welding the weld material is heated up, plasticized, joined under pressure and finally cooled off. There are many different welding techniques which primarily differ in there heat supply.


For ultrasonic-welding an ultrasonic-generator excites electrical oscillations, which anultrasonic-transducer (converter) dissipates into mechanical vibrations with the samefrequency. These oscillations then pass a transformation-adaptor (Booster) before reaching thesonotrode (welding-tool) which introduces them along the joint. Thereby the generator and the oscillating entity work together at resonance. The reflection of the mechanical oscillations at the acoustic-radiating surface of the sonotode creates a standing wave, which emits energy into the weld material.


The mechanical vibrations which reach the work piece under a certain contact pressure are absorbed and reflected at the interfaces. The resulting molecular- and interfacial-friction produces heat. The material starts to soften plastically and the area near the joint to be welded becomes sound insolating due to the plasticizing and the heavy absorbing of the plastic layers. This leads to a very intensive fusion penetration of the plastic, which means there action accelerates itself as an increasing amount of the oscillation energy dissipates into heat.


So, welding takes place via inner friction. After a certain clamping- respectively a certain cool-off-period while retaining contact pressure, the joining is completed.