(Click on the link above for a detailed technical discussion of ultrasonic welding)
Ultrasonic lamination uses the conversion of acoustic energy to heat to form spot welds of specific size in exact locations. This technique is an ideal method to join layers of different or similar materials (nonwovens, films, composites, or fabrics) into a single composite or laminate.
The layers of raw material are arranged and brought together as in any traditional lamination process to pass over a central rotating roll or “anvil” (see diagram above).
Instead of the uniform smooth surface roll used for pressure bonding, Ultrasonic Laminating uses an embossed pattern on the anvil or “pattern” roll. Each peak is the site of an individual weld across all layers of the lamination. The peaks are exactly shaped and located to yield the desired size and location of the weld.
Accoustic energy is generated from a “horn”. Each horn is individually powered so that its output can be exactly tuned to a series of pulses. Each pulse is a pressure wave that acts as a tiny hammer. The frequency of the pulses impacts the material tens of thousands of times per second over each peak location on the anvil. While all of the material passes under the horns, welding only occurs over the peaks of the anvil.
The degree of welding at each peak is determined by the nature of the material in the layers, the amount of energy applied from the horn, the size and shape of the peak, and the “dwell” time of the material in relation to the peak. The discrete bonding at specific points is an important feature of Ultrasonic Lamination, as it allows the unbonded materials to function as they were designed.
Ultrasonic Lamination is a non-contact and, therefore, a non-wearing process. As the layers to be laminated move across the dwell area, the layers are not stretched or pressured onto the anvil. For effective bonding, the layers need to be flat and almost lie in a relaxed state as they dwell over the peak, so the conversion of acoustic energy to heat for bonding is not dissipated or wasted.