Plastic and ultrasound welding: perfect union

Thermoplastic items are now widely accepted in almost every sector and they have now become part of our daily lives.

There are no limits to where they found. Try and think what our environment would be like without plastics.

Wide acceptance 

A car without these synthetic materials could not today be made, at least not at a viable cost.

In the food sector, plastic packagings allow easy transportation and preservation of food.

Toys, telecommunications, medical items, transportation and fabrics. There is no sector today that does not use plastics.

Choice of technology

It is therefore extremely important to analyse this dimension and all technological aspects that characterise it. The production of manufactured items and objects in plastic, whether mass produced or otherwise, requires careful technological evaluation that must follow the entire production process.

The designer must therefore ask what final objective needs to be achieved, what machinery should be used. The cost of production to obtain a certain object is the fruit of careful design and production choices. The assembly of thermoplastic parts is one of the many aspects that have to be studied with great care.

A number of technologies are available for assembling parts to create more complex objects.

The number one choice: ultrasound

Today, we are talking about one technology in particular: ultrasound welding.

The heat needed to melt the parts to be assembled is generated by an intense vibration. A few dozen microns of mechanical movement produced at high frequency (we are talking about frequency between 20 and 50 kHz) cause heating in a short period of time. An ultrasound generator moves a piezoelectric transducer. It transforms electrical energy into mechanical energy. This component is associated with a tool called a sonotrode which has the task of transferring the vibration to the parts to be assembled.

Ultrasound welding is fast and inexpensive. Moreover, it does not emit fumes due to reheating because only the weld part is plasticized. Energy consumption is modest. These characteristics means this technology is known and used widely in a production process linked to assembly. There are however circumstances where this technology is not preferable.

Choice of machinery

The use and choice of an ultrasound welder is established taking some important factors into account:

  • size and geometry of the pieces to weld;
  • type of thermoplastic used to make the parts;
  • output rate;
  • possible reuse of the machine for other applications;
  • investment cost.

The most suitable machine is decided based on these criteria and the dialogue between the user and manufacturer.

The welder range is notable, with power between 150 and 3000 Watts and with resonance frequency between 20 and 40 kHz. The choice of most suitable machinery becomes fundamental for the assembly of the parts in accordance with the project. Moreover, the use of the machine for other applications shortens the amortisation times.


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Sirius Electric S.r.l.
Via Mastronardi 6/b
27029 Vigevano (PV) Italy
Tel. +39 0381 32.56.10 - 31.25.22
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