Sonic welding or ultrasonic welding services is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to materials being held together under pressure to create a solid-state weld. It is most commonly used for plastics, and especially for joining dissimilar materials. In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together.
For joining plastic materials, ultrasonic welding equipment can be easily customised to fit the exact specifications of the materials being welded. The parts are sandwiched between a fixed shaped nest (anvil) and a sonotrode (horn) connected to a transducer, and a ~20 kHz low-amplitude acoustic vibration is emitted. (Note: Common frequencies used in ultrasonic welding of thermoplastics are 15 kHz, 20 kHz, 30 kHz, 35 kHz, 40 kHz and 70 kHz). When welding plastics, the interface of the two parts is specially designed to concentrate the melting process. One of the materials usually has a spiked energy director which contacts the second plastic part. The ultrasonic energy melts the point contact between the parts, creating a joint.
Ultrasonic welding of plastics causes local melting of the plastic due to absorption of vibrational energy along the joint to be welded. Ultrasonic welding services can be used for both hard and soft plastics, such as polypropylene.
Ultrasonic welding machines also have much more power now. The understanding of ultrasonic welding has increased with research and testing. The invention of more sophisticated and inexpensive equipment and increased demand for plastic components has led to a growing knowledge of the fundamental process. However, many aspects of ultrasonic welding still require more study, such as relating weld quality to process parameters. Ultrasonic welding continues to be a rapidly developing field.
The benefits of ultrasonic welding services are that it is much faster than conventional adhesives or solvents. The drying time is very quick, and the pieces do not need to remain in a jig for long periods of time, waiting for the weld to dry or cure. The welding can easily be automated, making clean and precise joints. The site of the weld is very clean and rarely requires any touch-up work. The low thermal impact on the materials involved enables a greater number of materials to be welded together.