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Telsonic in Switzerland has developed the Soniqtwist technique to eliminate the problems associated with the conventional process of using ultrasonics for welding, joining and sealing.

The characteristics of the conventional process, which produces amplitude in the vertical plane, has, until now, however, limited the use of the technology for certain applications within the electronics or medical-device industries.

This has been largely owing to concerns over possible damage to fragile electronic components or perforation of micron thin seals and membranes.

The Soniqtwist technique uses small circumferential amplitudes and allows even the most delicate electronic components and membranes to be joined, welded or sealed.

Thin films and membranes, which have a typical thickness of 50 microns, are used to create a hermetic air-tight seal on medical pots, devices, containers and drug delivery systems.

The company claims that it is essential, therefore, that any process used to weld the delicate film or membrane media does not induce any defects or damage.

The vertical amplitudes produced across the face of a sonotrode or horn, when using conventional ultrasonic welding techniques, cause a diaphragm effect when welding a thin film or membrane.

This, in turn, may result in perforation of the membrane, effectively rendering the conventional ultrasonic welding process unsuitable for this type of application.

Soniqtwist, however, produces small amplitudes of typically 60 microns pp in a circumferential manner at the perimeter of the seal, with the torsional amplitude diminishing to almost zero at the centre of the membrane or film.

The technique does not stretch the membrane during welding, nor does it cause a diaphragm effect or induce perforation of the film, according to the company.

The Soniqtwist technique therefore effectively eliminates the risk of perforation when welding polymer-based foils, films and membranes.

Complete weld cycles can be achieved in less than a second.

The characteristics of Soniqtwist also enable multiple membranes, in close proximity to one another, to be processed without causing any previously welded membrane to become dislodged or to lose its hermetic seal.

The process is suitable for a range of welding and forming operations on thin wall section components in a variety of materials, including plastics, ceramics and aluminium.

The technique also minimises particle production and size, supporting good automated manufacturing practice requirements in the medical-device manufacturing sector.

The benefits of Soniqtwist can also be applied to welding operations on housings that contain delicate electronic devices that must not be damaged or affected during welding.

The process is not limited to circular parts; rectangular and non-symmetrical-shaped components can also be welded, sealed and joined.

Conventional ultrasonics techniques feature the converter, operating at between 20kHz and 35kHz, mounted on top of a booster to increase the amplitude.

The sonotrode or horn is, in turn, coupled to the booster, which utilises the lower cross-sectional area of the sonotrode working face to further magnify this amplitude.

By using a pneumatic actuator in conjunction with the energy being delivered via the sonotrode, the process creates local heat and melt.

The vertical force from the pneumatic actuator force collapses the molten joint and holds it in position until the weld joint has solidified.

With the Soniqtwist principle, the converter is mounted tangentially to the booster axis, thus creating reciprocal circumferential amplitude to the specially designed sonotrode.

The Soniqtwist process creates a reciprocating ultrasonic friction weld of the upper contacted film, membrane or rigid part component about the lower component part.

The vertical force from the electronic proportionally controlled pneumatic actuator used in the Soniqtwist configuration collapses the molten joint and maintains the required pressure until the weld joint has solidified.

The Soniqtwist welding head can be retrofitted to a standard bench-top machine.

The head can also be mounted to pneumatic actuator modules or servo-operated actuators, enabling incorporation within a fully automated assembly machine.

The Soniqtwist configuration can also be used in multi-head applications.

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