How Is The Heat Of The Ultrasonic Welding Machine Generated?

Ultrasonic welding technology has the advantages of economy, reliability, and easy automation integration, and is a common technology for plastic welding.

Unlike traditional heat sources that generate heat in direct contact with plastic, ultrasonic copper connections generate heat by spraying.

1. Amplitude, frequency and wavelength

In ultrasonic welding, longitudinal waves propagate at high frequencies, resulting in low-amplitude mechanical vibrations. The electrical energy of the welding machine is converted into mechanical energy for reciprocating motion. To understand the relationship between amplitude, frequency, and wavelength, and how they relate to heat generation, we need to identify the main components of an ultrasonic welder.

The main components of an ultrasonic welder are a power source, a transducer, an amplitude modulator (sometimes called an amplitude converter) and a welding head. The generator converts a 50-60Hz power supply with a voltage of 120V/240V to a 20-40khz power supply with a voltage of 1300V. This energy is fed into the sensor, which converts the electrical energy into mechanical vibrations using a disk-shaped piezoelectric ceramic that produces a strain displacement when a high-frequency current is passed through it.

The transducer transmits the vibration to the amplitude modulator. The amplitude modulator amplifies the amplitude of the ultrasonic waves and continues to transmit it to the welding head. The solder tip continues to amplify the amplitude of the ultrasonic waves and makes contact with the part.

The energy is transferred to the welding rod locations of the two parts of the assembly. Since the electrode is designed to be a point where energy is concentrated, friction generates heat under pressure. Heat is generated by friction between the upper and lower surfaces of the material and between the molecules within the material. The heat from the friction melts the upper and lower parts and joins them together at the welding location.

2. Know the heating rate

For the same material, three factors determine the heating rate: frequency, amplitude and welding pressure. For existing devices such as 15Khz, 20Khz, 30khz or 40Khz, the frequency is fixed. Therefore, the heating rate can usually be changed by the welding pressure. In general, the higher the pressure, the faster the heating rate. Also, you can change the amplitude, just like the pressure, the higher the amplitude, the faster the heating.

Of course, excessive pressure and amplitude can also adversely affect weld quality, such as material degradation, leaks, cracks and spills. Therefore, ultrasonic welding requires a process of process parameter optimization. After the welding process parameters are determined, the welding process can achieve stable output of high speed and high strength. This is why ultrasonic welding is widely used in mass production.

3. Time, distance, power and energy

The heat required for welding depends on the material type, weld design and equipment specifications. The traditional thermal control method is welding according to the time mode, that is, welding for a certain time, such as 0.2-1s (generally less than 1s). However, today's ultrasonic welding equipment often also allows setting and monitoring of welding distance, power and energy. Properly trained operators can also adjust parameters for consistent welding results based on actual conditions and different materials. This also greatly improves the flexibility and reliability of welding.