How does the ultrasonic welding machine generate heat?

 Ultrasonic welding technology has the advantages of economy, reliability, easy automatic integration, etc., is a common technology in the field of plastic welding. Unlike the heat generated by direct contact with the traditional heat source, ultrasonic welding generates heat through friction.

Amplitude, frequency and wavelength In ultrasonic welding, the P-wave propagates in a high frequency manner, producing a mechanical vibration of low amplitude. The electrical energy of the welding machine is converted into mechanical energy of reciprocating motion. In order to understand the relationship between amplitude, frequency and wavelength, as well as their relationship with heating, we need to understand the main components of the ultrasonic welding machine.

The main components of the ultrasonic welding machine are the power generator, the transducer, the amplitude modulator (sometimes called the horn) and the welding head. The power generator converts a 50-60Hz power supply with a voltage of 120V/240V to a power supply with a voltage of 1300V and an operating frequency of 20-40Khz. This energy is supplied by a transducer, which uses a disc-shaped piezoelectric ceramic to convert electrical energy into mechanical vibration, i.e. when a high-frequency current passes through the piezoelectric ceramic, the piezoelectric ceramic creates a strain displacement.

The converter transmits the vibration to the modulator. The modulator amplifies the amplitude of the ultrasonic wave and continues to transmit it to the welding head. The welding head continues to amplify the amplitude of the ultrasonic wave and makes contact with the part.

Energy is transferred to the assembly of two local welded rib locations. Because the welded ribs are designed with pointed points, the energy is concentrated at the pointed points, and the friction generates heat under pressure. This heat is generated by two kinds of friction, one external friction between the upper and lower parts of the data, and the other intermolecular friction within the data. It is the heat generated by friction that causes the upper and lower parts to condense and join together at the welding position.

Understand the heating rate

For the same data, there are three factors that determine the heating rate: frequency, amplitude, and welding pressure. With respect to existing equipment, such as 15Khz, 20Khz, 30Khz or 40Khz machines, the frequency is fixed. Thus, the heating rate can usually be changed by the welding pressure. In general, the higher the pressure, the faster the rate of warming. In addition, the amplitude can be changed, as the pressure changes, the greater the amplitude, the faster the heating rate.

Of course, too much pressure and amplitude will also have an adverse effect on the quality of welding, such as data degradation, leakage, cracks and flash. Therefore, ultrasonic welding requires a process to optimize the process parameters. After the parameters are confirmed, the welding process can reach a stable output, and the welding speed is fast and the welding strength is high. This is the reason why ultrasonic welding is widely used in mass consumption.

Time, interval, strength and energy

The amount of heat required for welding depends on the data type, welding design, and equipment specifications. The traditional way to control heat is to weld in the form of time, that is, to weld for a certain time, such as 0.2-1s(generally less than 1s). However, conventional ultrasonic welding equipment is often able to set and monitor welding intervals, power and energy. Properly trained operators can also adjust parameters according to practice conditions and different data to achieve divergent welding results. This also greatly improves the sensitivity and reliability of welding.