The influence of ultrasonic transducer on ultrasonic welding
Ultrasonic welding specifications, especially the amplitude of ultrasonic vibration and the frequency of output current, have a great influence 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 kind of welding is produced when the ultrasonic vibration power is not large. Because, in order to obtain the amplitude that can guarantee the welding quality, we must weld under the conditions close to resonance. Of course, in this case, even if the natural frequency of the mechanical vibration system does not change much, the amplitude will be significantly reduced.
Since the welding quality is very sensitive to changes in external conditions, the quality of the resulting joint is very unstable. Under actual welding conditions, since a sufficiently strong joint is formed between the two weldments under the vibrating head and on the surface of the worktable, the natural frequency of the vibrating system will also change significantly.
As the power of the ultrasonic transducer increases, the amplitude changes during the ultrasonic welding process will correspondingly decrease, so the strength of the joint will have greater stability. This situation can be explained by two reasons: 1. The change in load has a relatively small impact on the high-power ultrasonic transducer; 2. Because the connection joint at a contact point is continuously damaged, the connection is transmitting vibration The mass of the object on the rod is relatively small. Therefore, the power of the ultrasonic transducer can be increased to improve the stability of the joint quality.
The relationship between the amplitude and the change of the natural frequency of the system that we have discussed will only appear when the frequency of the generator output current remains unchanged. When the frequency of the current changes occasionally, the change characteristics of the amplitude will become very complicated, so that 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 conditions 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.
