What is Ultrasonic Welding?
Ultrasonic plastic welding is the joining or reforming of thermoplastics through the use of heat generated from high-frequency mechanical motion. It is accomplished by converting high-frequency electrical energy into high-frequency mechanical motion. That mechanical motion, along with applied force, creates frictional heat at the plastic components’ mating surfaces (joint area) so the plastic material will melt and form a molecular bond between the parts. The following drawings illustrate the basic principle of ultrasonic welding.
When a rubber ball is dropped, it never bounces back to its drop height because some of the potential energy is converted to heat and sound. This type of process is involved in ultrasonic welding. Instead of a ball, a small projection(s) in the weld zone is flexed by an oscillating force at rates of 10,000 to 70,000 times per second (kHz). This causes the projection to melt and flow across the joint to create a weld. A metal tool (horn) that is oscillating vertically contacts the plastic part at a distance from the projection and is the means for delivering the energy. The part on the other side of the joint area rests on an anvil, ensuring the energy is spent in the weld zone. Frictional heating can also occur to some extent because transmission of the energy through the plastic parts is very complex. How ultrasonic welding is used to bond thermoplastics? The oscillating force is generated when alternating electrical power (at frequency) is applied to a train of tuned components that
Employing vibration, force and time, an ultrasonic welder forms a weld by pressing the parts to be joined together and scrubbing them against one another to break up and disperse the surface oxides and contaminates. The resultant clean base metal surfaces are held tightly together. Crystal boundaries are brought within atomic distance of one another allowing the strong attraction of atoms across the interface to create a metallurgical bond without reaching the melt temperature of the metals being joined. Since ultrasonic metal welding does not depend on achieving a melt of the metals to be joined, their melt temperatures and their thermal conductivity are not process factors. The entire welding process is accomplished in approximately 250 ms.
Ultrasonic welding is a process of joining two parts to one another by the use of high frequency sound waves. This operation is usually performed on parts made of a thermoplastic material and is a fast and reliable way of joining two parts together. On an ultrasonic welding machine electrical energy is converted to heat energy by high frequency sound waves which then are converted to mechanical energy and is then channeled through a tool called a horn. The horn transfers the mechanical energy onto the part. The part is then placed on a fixture and then the horn is lowered at a set pressure on the part and the welding process begins. The vibrations generated heats up and causes subsequent melt where parts join. This results in a strong molecular bond between the two parts.
