What are the main components of an ultrasonic welding machine? How does the ultrasonic welder generate heat?
The main components of the ultrasonic welding machine are the power generator, the transducer, the amplitude modulator (sometimes called the amplitude rod) and the welding head. The power generator converts a power supply with a voltage of 50-60Hz and a voltage of 120V/240 V into a power supply that runs at 20-40 Khz and a voltage of 1300 V. This energy is provided to the transducer, which uses a disc-shaped piezoelectric ceramic to convert electrical energy into mechanical vibration, that is, when a high-frequency current passes through the piezoelectric ceramic, the piezoelectric ceramic generates strain displacement.
The converter transmits the vibration to the amplitude modulator. The amplitude 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 comes into contact with the component.
The energy is transferred to the welding rod position of the assembled two parts. Because the welding ribs are designed with sharp points, the energy is concentrated at the sharp points, and friction and heat are generated under pressure. Heat is generated by two kinds of friction, one is the surface friction between the upper and lower parts of the material, and the other is the internal molecular friction of the material. It is because of the heat generated by friction that the upper and lower parts melt and join together at the welding position.
For the same material, there are three factors that determine the heating rate: frequency, amplitude and welding pressure. For existing equipment, such as 15 Khz, 20 kHz, 30 Khz or 40 Khz, the frequency is fixed. Therefore, the heating rate can usually be changed by welding pressure. Generally, the higher the pressure, the faster the heating rate. In addition, you can also change the amplitude, like the pressure, the greater the amplitude, the faster the heating speed.
Of course, excessive pressure and amplitude will also have a negative impact on welding quality, such as material degradation, leakage, cracks and overflow. Therefore, ultrasonic welding requires an optimization process of process parameters. After determining these parameters, the welding process can reach a stable output, and the speed is high, and the welding strength is strong. This is the reason why ultrasonic welding is widely used in mass production.
The amount of heat required for welding depends on the type of material, welding design and equipment specifications. The traditional method of controlling heat is through time, that is, welding for a certain time, such as 0.2~1s (generally less than 1s). However, today's ultrasonic welding equipment can also set and monitor welding distance, power and energy. In properly trained operators, the parameters can also be adjusted according to the actual situation and different materials, so as to obtain a consistent welding effect. This also greatly improves the flexibility and reliability of welding.
