What are the four common parameters of ultrasonic welding machine
The principle of ultrasound is that the generator will generate 20KHz (or 15KHz) high-voltage and high-frequency signals. The signal is converted into high-frequency mechanical vibration by the energy conversion system, which is applied to the plastic workpiece, passing through the surface of the workpiece and between the molecules. Friction increases the temperature transferred to the interface. When the temperature reaches the melting point of the workpiece itself, the interface of the workpiece will melt rapidly, and then fill the gap between the interfaces. When the vibration stops, the workpiece is cooled and formed under a certain pressure to achieve high-quality welding. The four basic parameters of the ultrasonic welding machine are as follows:
1. Ultrasonic frequency
The vibration frequency is determined by the natural frequency of the mechanical system. For general equipment, unless there are special needs, its size is actually always constant. When selecting the vibration frequency, the nature and thickness of the welding material should be considered. When the thickness of the welding material is reduced, try to use higher frequency ultrasonic waves. In this case, increasing the frequency is a way to reduce the amplitude without changing the sound power. After reducing the amplitude, the positive and negative alternating stress acting on the weldment will also be reduced, thereby reducing the risk of fatigue damage. This risk is very high when welding extremely thin weldments. As the height increases, the vibration energy consumed in the process of transmitting vibration to the weld will also increase. It can be seen that when welding thick weldments, low-frequency ultrasonic vibration should be selected.
2. Welding pressure
The contact pressure ensures that the transmission of ultrasonic vibrations can be achieved, and at the same time, the metal generates the plastic flow required to form the joint. For weldments of different materials and thicknesses, the lower limit of the contact pressure required to form the joint is not equal. Its size increases with the increase in the flow limit, hardness and thickness of the weld metal. Generally reasonable contact pressure values also increase with the increase in amplitude.
3. Ultrasonic welding time
According to the nature of the material, thickness and some other parameters, the welding time has different values, usually not more than 4 seconds. The change in welding time related to the properties and thickness of the weld metal is related to the change in contact pressure.
4. Ultrasonic amplitude
Amplitude is the basic parameter of ultrasonic welding. It determines the removal of the surface film, the size and location of the plastic deformation zone and the degree of heating, and therefore determines the quality of the resulting joint. For an ultrasonic horn with a certain amplification factor, its amplitude can be determined by changing the output voltage parameter of the generator. When welding, the amplitude is determined according to the nature and thickness of the material, ranging from 5 to 25 microns.