The Ultrasonic welding is to convert electricity into a high-frequency, high-voltage signal through the electrical box, and then to a high-frequency mechanical vibration through the transducer system, which is applied to plastic products, when the temperature reaches the melting point of the product itself, the interface of the product melts rapidly, and at the same time the product is cooled and shaped under a certain pressure, to achieve a perfect fusion
Ultrasonic welding specifications, especially the amplitude of ultrasonic vibration and the frequency of output current, have a great impact on the stability of joint quality. It has the welding characteristics of the first thermal cycle, and the stability of the amplitude is the lowest. This welding occurs when the ultrasonic vibration power is small.
In order to obtain the amplitude that can guarantee the welding quality, the welding must be carried out under the condition close to the resonance. Of course, in this case, even if the natural frequency of the mechanical vibration system changes little, the amplitude will be significantly reduced.
Because the welding quality is very sensitive to the change of external conditions, the quality of the obtained joint is very unstable. Under the actual welding conditions, the natural frequency of the vibration system will also change significantly because a sufficiently firm joint is formed at the contact between the two weldments under the vibration head and the surface of the workbench.
With the increase of the power of the ultrasonic transducer, the change of the amplitude in the ultrasonic welding process will be correspondingly reduced, so the strength of the joint will have greater stability. This can be explained for two reasons:
1. The change of load has little influence on the high-power ultrasonic transducer;
2. The mass of the object connected to the vibration transmission rod is relatively small due to the continuous damage of the connection joint at the contact point of a certain contact point. Therefore, the stability of the joint quality can be improved by increasing the power of the ultrasonic transducer.
The relationship between the amplitude and the change of the natural frequency of the system discussed above will only appear when the frequency of the generator output current is constant. When the frequency of the current changes occasionally, the variation characteristics of the amplitude will become very complex, so the quality stability of the joint will be reduced.
When there is a generator that can automatically adjust the current frequency according to the natural frequency of the vibration system, the working stability will be completely different. Under the working condition of the stabilizer, the amplitude is very stable and reaches the maximum value of the transducer, which improves the stability of the joint quality. When we adjust the generator to the same power, we can weld thicker weldments.