Often, you can connect different materials with fasteners such as nails, screws, or threads, and this works with metal, wood, fabric, and plastic. Many plastics use glue, which forms a chemical bond between the glue itself and the surface of the plastic material being bonded. Metals can be bonded together by heating other metals to act as binders, such as lead solder in electrical connections. Alternatively, the metals can be melted directly together, and once the surface of the melted metal cools, the metals join together. Welding usually requires an open flame or torch to achieve the high temperatures necessary to melt the metal surface. Therefore, welding is an expensive process for some manufacturing industries.
A new and more economical welding method was introduced in the 1940s - ultrasonic welding. Ultrasonic welding technology uses the vibration of high-frequency sound waves to join different materials together. By applying ultrasonic vibrations to the contacts, the high-frequency vibrations cause the material to melt. The typical frequency range used in ultrasonic welding is between 15 and 40 kHz. ---Pinghe ultrasonic spot melting machine