Ultrasonic mold design is a very complex task, which needs to be considered comprehensively according to the mold material, size, machine frequency, and acoustic principles. Simply put, the purpose of ultrasonic mold grooving is to destroy the transverse waves generated in ultrasonic transmission. Generally, the grooving is at 1/2 the wavelength of the transverse wave, which is mainly considered based on the principle of acoustics. As for why the mold has to be made with different widths between the top and bottom, the main consideration is to increase the output, and the principle is similar to amplifying the output of sound waves. A good mold is the most important prerequisite for stable welding. If the mold design is not good, it will cause a series of welding problems, such as uneven welding, mold heating, noise, and even cracking!

    The longitudinal resonance frequency of the ultrasonic mold is its working frequency. It must be consistent with the resonance frequency of the transducer vibration system, otherwise the longitudinal working efficiency of the vibration system will decrease. The lateral resonance of the tool must be suppressed as much as possible. The vibration of the mold can be divided into the following three states:

    (1) The transverse dimension of the ultrasonic mold is much smaller than the longitudinal dimension, and generally requires more than 2 times, that is, l,≥2lx, l,≥21y, and the transverse resonance frequency is much higher than its longitudinal resonance frequency. Therefore, the transverse vibration has no effect on the longitudinal vibration. Why is the ultrasonic mold grooving tool vibration similar to the one-dimensional longitudinal vibration of a slender rod along the Z direction? At this time, one-dimensional theory can be used to design the ultrasonic mold to meet the practical accuracy requirements.

(2) The two horizontal dimensions of the tool are comparable to the longitudinal dimensions. At this time, the sound wave radiation surface of the tool is a large-sized short-shaped surface with little difference in length and width. The longitudinal resonance frequency of the tool and its two transverse resonance frequencies Relatively close. In this case, due to the influence of the Poisson effect, while the tool resonates longitudinally, it also produces strong vibrations in its two transverse directions. The inter-combination of longitudinal vibration and lateral vibration changes the longitudinal vibration state of the tool. At this time, if one-dimensional theory is still used to calculate and design the tool, there will be large errors in theory and experiment. Therefore, the above must be used. The detailed vibration theory studies the three-dimensional coherent vibration of tools. And in order to ensure the working efficiency of the tool and the uniformity of the displacement distribution on the radiation surface, the lateral vibration in the two directions must be effectively suppressed.

    (3) Among the two lateral dimensions of the mold, one of them is much smaller than the longitudinal dimension of the mold, that is, it satisfies 12) 21, (or l,), but the other lateral dimension of the mold is larger, which is close to or exceeds the longitudinal dimension of the mold. At this time, the radiation surface of the sound wave is a long and narrow rectangular surface, and the lateral vibration in the direction corresponding to the smaller size can be ignored, but the lateral resonance frequency and the longitudinal resonance frequency in the direction corresponding to the larger size are relatively close. interaction. Therefore, the lateral vibration in this direction has a greater influence on the longitudinal direction. At this time, one-dimensional theory is no longer applicable, and hybrid vibration theory must be used to analyze, research and design such systems, and this lateral vibration should be suppressed.

    In order to effectively suppress the transverse vibration of the tool, the longitudinal and transverse resonant frequencies of the ultrasonic mold must first be calculated using the frequency equation, and the transverse vibration mode closest to the fundamental frequency of the longitudinal vibration of the ultrasonic mold must be suppressed by grooving. The slot must be located at the node of the transverse vibration mode of the ultrasonic mold, and the size of the slot should be selected reasonably. In order to be economical and effective, the strongest transverse vibration should be suppressed. Only in this way can the transverse vibration of large-sized tools be effectively suppressed, and Improve the uniformity of the displacement distribution of the acoustic radiation surface of the ultrasonic mold, improve the longitudinal working efficiency of the ultrasonic vibration system, and achieve the ideal ultrasonic welding effect.