Ultrasonic Welding

Ultrasonic welding is uses friction to heat the parts being welding (not to be confused with friction welding).  In ultrasonic welding, the parts being welded are clamped together between a stationary anvil and a vibrating horn.  The horn vibrates at ultrasonic frequencies and hence the name Ultrasonic welding.  This process is commonly used for welding certain thermoplastics and soft metals.  The inner workings of the power supply used for welding is the same for both plastics and metals.  The difference is in the way which the energy is delivered to the parts.  To weld metals, the horn vibrates parallel the weld interface; for plastics, the horn vibrates perpendicular to the weld interface.

The fundamentals of the processes are often confused with friction welding, since it appears that the two metal parts are being rubbed against each other.  In reality the parts do not have any relative motion between the two at the weld interface.  The heat, and subsequent softening, is produced by internal friction, i.e., the atoms of the parts vibrating against each other at high frequency and amplitude.  Once the parts are softened, the atoms across the interface are brought in intimate contact by the action of the welding force and are able to form a solid-state bond.

Ultrasonic welding is not a cold welding processes.  The parts do get quite hot, though not as hot as in other fusion welding processes.  The critical parameters for metal ultrasonic welding are:

1.  Ductility of the metals being welded

2.  Size of the metal piece in contact with the vibrating horn

3.  Surface cleanliness and coatings

If you need help with any aspect of the ultrasonic welding process, please contact us for more details.