Ultrasonic welding
Ultrasonic welding is a process that can be used to join plastics. It can also be used to weld metals. For example, this process is used in electrical engineering to wire microchips.
The heat required to melt the materials is generated by high-frequency mechanical vibrations during ultrasonic welding. These vibrations are generated by the ultrasound in the materials themselves. The heat is generated by molecular friction within the components. This also means that ultrasonic welding can be categorised as a friction welding process.
Welding - Devices
Several devices or assemblies are required for the process. These include a generator, an oscillating structure, for example a converter, and an anvil. The generator has the task of generating the ultrasonic frequency. To do this, it converts the existing mains voltage into a high voltage with a high frequency.
A shielded cable then transmits the electrical energy to the converter, which acts as an ultrasonic transducer. The converter utilises the piezoelectric effect, according to which crystals expand and contract again within an alternating field. This causes a mechanical oscillation. The oscillation is then transferred to the probe used via an amplitude transformer.
The sonotrode is now used to direct the generated vibrations onto the material by means of pressure. Molecular friction now occurs in the material, which then leads to the generation of heat.
When ultrasonically welding plastic, the increased temperature at the point of contact causes the plastic to soften. This leads to an increase in the damping factor of the material, which in turn increases the heating. This results in a cycle that causes a rapid increase in heat. This results in very short welding times, which in turn ensures the cost-effectiveness of the process.
Other welding processes:
