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Ultrasonic technology used in the manufacture of wearable medical device

The ongoing COVID-19 pandemic has required an agile response from

not only the NHS but also the manufacturers of the personal protection

equipment, medical devices and monitoring systems required to treat

seriously ill patients.

Achieving the high volumes required, has in turn, generated an increase

in demand for the technologies used to produce these essential items,

including ultrasonic systems used for performing welding processes.

Telsonic has been pro-active in assisting both end user manufacturers and

automation machine builders by providing the modules, systems, tooling

and technical support needed to respond quickly to these unprecedented


In a recent application, Telsonic UK has supplied a complete twin head ultrasonic

welding station, integrated as part of the manufacturing process for a wearable

therapy device. This battery powered disposable device, similar in size to a small

wristwatch, is attached to the patients leg and sends out electrical impuLses that

reduce the risk of Venous ThromBoembolism, a dangerous blood clot condition

suffered by almost one third of seriously ill coronavirus patients. As a result, the

NHS has ordered thousands of these potential life saving devices.

The device is manufactured by Firstkind Ltd, a UK based science-led medical

devices company who manufacture a range of non-invasive geko™ branded

products with an embedded ground-breaking NMES technology platform.

Neuromuscular electrical stimulation (NMES) is a treatment using electricity

to stimulate muscles and nerves, helping to improve flexibility, strength, and


The ultrasonic welding technology supplied by Telsonic for this application has been integrated as part of a comprehensive pallet line automation system, built in-house by Firstkind. The device casing is manufactured in Polypropylene and the ultrasonic system is used to precisely stake four hollow pins into moulded recesses, effectively attaching the back onto the device, thus enclosing the internal assembly and sealing the battery in


Components are presented on twin cavity pallets for processing by Telsonic’s twin head installations. Each ultrasonic system comprises of a MAG3512S generator, an air cooled precision adjustable and spring loaded integrated SE3512VF converter module together with a Titanium booster mounted to a Telsonic AC450 pneumatic actuator with a Titanium 4 point single body sonotrode. The sprung loaded head assemblies deliver a controlled staking action, allowing the material to flow at a low part reactive closure force. Weld delivery control is determined by precise weld and hold time from the machine’s main PLC.

The challenge presented by the weld specification dictates that the ultrasonic welding process has to produce an aesthetically pleasing result whilst achieving a tight closure gap between the parts. In addition, to ensure patient comfort, the weld must be constrained sub flush within the recesses. The component assembly retention strength has to be fit for purpose whilst in use, offering anti-tamper proofing, yet ultimately allowing

disassembly for battery removal after use for recycling and disposal purposes. The application requirement for multiple stake positions welded simultaneously on one tool requires pin/recess moulding design in collaboration with precise sonotrode tool face design and actuator force delivery.

In addition to the technical challenges surrounding the application, timescales were extremely important to get the weld station completed ready for the line installation and in production as quickly as possible.

To adhere to COVID rules, the factory acceptance test (FAT) at Telsonic UK was conducted remotely and successfully with Firstkind using PC based visual tools.

Experience of this type of application, underpinning Firstkind’s confidence gained in the weld solution proposed, together with Telsonic’s pro-active engagement throughout the project, relating to material selection, joint design, and process integration, were contributory factors in Telsonic securing this business.

SOURCE:By Martin Frost, Telsonic UK Limited and Tom Pettit, Genesis Sales & Marketing Limited