How to track and control the frequency of ultrasonic welding machine?
The transducer of the ultrasonic welding machine vibrates at the unloaded resonance frequency, which is approximately pure resistance, but once the load changes, the equivalent circuit parameters of the transducer will change, and the actual operating frequency is different from the power supply resonance frequency. At this time, the welding efficiency is Low, the welding quality and effect are affected, and the welding machine is also easily damaged. Therefore, the automatic tracking of the resonant frequency must be considered when designing the circuit.
After determining the operating frequency, power generally needs to be considered. There are generally several power levels for each workpiece frequency. For example, with a working frequency of 20 kHz, the power range of ultrasonic welders provided by most equipment manufacturers is 1~5Kw. In most cases, the required power can be determined through experiments by suppliers, research institutions, and university laboratories. If the required power cannot be determined in advance in theory, select high power to ensure that the device can meet the application requirements.
The choice of ultrasonic welding equipment is a very complicated issue, and we should consider various factors at the same time. Therefore, the purpose of this section is to provide general guidance for equipment selection, and the actual equipment selection should be in close contact with ultrasonic welding experts or equipment suppliers and listen to their opinions.
When choosing an ultrasonic welding machine, one of the key factors is the operating frequency. The operating frequency range of most equipment on the market is 20 kHz≤40 kHz, and the operating frequency of some equipment is 10×70 kHz. The use of low amplitude for ultrasonic molds/thin-wall welded parts helps to reduce the resonance of the weld, because most of the resonance will cause damage to the welded parts. Increasing the operating frequency or vibration amplitude will increase the power loss of the polymer. Therefore, in most cases, using a higher operating frequency is a feasible method to obtain lower amplitude and higher power.
Similarly, when selecting equipment, it is necessary to determine whether the welded parts are suitable for cutting or continuous welding. In the case of seam welding, most equipment manufacturers have such standard equipment, and they can also provide patterns for many other standard rotating anemones. Most anvils are cut, sealed and welded. If the weld requires very wide continuous welding (from 130 px to 3050 px), special equipment must be designed.
Other equipment factors include control level, amplitude control, amplitude profile and stored program control capabilities. In some applications, these options can improve welding quality and density. On the other hand, testing in an application laboratory can help determine which options are needed. It should also be noted that for most equipment manufacturers, some additional options can be added to the welding equipment after purchase.