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Ultrasonic welding is a rapid and economical technique for joining plastic parts. It is an excellent technique for assembly of mass produced, high quality products in plastic materials.

Branson informs about Ultrasonic Welding

Welding thermoplastic materials by means of ultrasonics has quickly become an established method, thanks to the continuous development of the plastics trade and the clean, simple application of this technology. The ultrasonic welding enables a safe and above all long-living connection of different products. The feature of a permanent joint – i.e. the conscious decision to forfeit the option of future disassembly and repair – for common consumer products, has also contributed. Another important area of application is the manufacturing of disposable products for hygienic purposes, for example in the field of medicine.

 

From generating to using the ultrasonics, four different phases can be distinguished: 

  1. Electrical ultrasonic vibrations in the frequency range from 20 to 40 kHz are generated by an ultrasonic power supply that is fed with normal 50-Hz mains current.
  2. A post-connected converter converts the high-frequency electrical vibrations, delivered from the power supply, into mechanical vibrations – comparable with ultra-fast hammering.
  3. The constant amplitude delivered by the converter is adjusted by the booster, in accordance with the needs of the application.
  4. Ultimately, the horn transmits the high-frequency vibration energy to the welding surface.

 

Under the influence of an applied force, the vibrations introduced are converted into thermal energy (latent heat of fusion) via frictional motion of the interfaces and the absorption of ultrasound waves: Material from both the welding parts merge in the weld zone and forms a near homogenous joint after it has cooled down. The molten material, and therefore the resultant seam strength, can be positively influenced by means of amplitude or force profiling.

Commercially available ultrasonic systems function according to this principle: compact units, standard machines or complete and specially constructed concepts for modern series production. The method is fast, efficient, and environmentally friendly, because no additives are needed.


Apart from surface welding, the ultrasonic process can be utilized for staking, flanging, spot welding or to insert metal sockets in the material. Other established uses are cutting and edge-sealing of thermoplastic films/fabrics, as well as residue-free slicing in industrial food production.

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