Ultrasonic welding is one of the common plastic welding processes in the industry. The three most important parameters of this process: amplitude, duration (welding time) and force (welding pressure). Welding time and pressure are parameters that are easy to adjust later in the process development. The amplitude is often determined in the early stage of development and difficult to change in the later stage, so a suitable amplitude must be designed in advance.
A typical welding head design method is: under the condition of lower than the material fatigue limit stress, the larger the welding head design transformation ratio, the better (that is, the larger the output amplitude, the better). If you need to reduce the amplitude, replace the amplitude modulator with a smaller ratio or adjust the voltage to reduce the amplitude.
How to control the minimum amplitude required:
1. It is impossible to evenly distribute the transformation ratio, that is, the transformation ratio of the welding head and the amplitude modulator are very different. It should be noted that when the welding head and the amplitude modulator have a close transformation ratio, the performance of the ultrasonic triplet (transducer + amplitude modulator + welding head) will be improved.
2. Reduce the welding head transformation ratio by changing the voltage, and at the same time reduce the maximum output power of the electric box. For example, when the amplitude is set to 50%, an electric box with an original output power of 2400W will actually output 1200W. It is easy to cause overload.
3. Using large amplitude will cause unacceptable damage to parts. For example, cracks in a small cross-sectional area may cause burns in appearance, and may cause damage to membranes, filter membranes and electronic components.
Due to the above reasons, it is very important to define the minimum amplitude required for ultrasonic welding of plastics.
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