The importance of matching between ultrasonic transducer and ultrasonic generator
Let the ultrasonic transducer and the ultrasonic generator drive power supply and the ultrasonic mold cooperate to form a complete ultrasonic equipment can be referred to as matching for short. Since the impact of matching on the performance of the whole machine is decisive, the importance of matching cannot be overemphasized. The main consideration for matching is the capacitance of the ultrasonic transducer, followed by the frequency of the transducer.
It needs to be emphasized that the ultrasonic transducer itself is not an energy generator, it is just an energy converter. It converts electrical energy into sound energy (mechanical energy). Under the premise that the input (drive power) and output (amplifier, ultrasonic mold) are well matched, it can convert (output) a large amount of energy.
Input matching refers to the matching between the ultrasonic transducer and the ultrasonic power supply. If the output matching is good but the input matching is not good, the transducer is weak and the welding is not strong. If the output matching is not good but the input matching is good, the transducer will be overloaded, causing chip dislocation, cracking, breakage, screw breakage, aluminum cracking or burning the power tube of the electric box. For example, if a car slams on the accelerator in neutral, the engine must be easily damaged.
There are four main aspects to the matching between the ultrasonic transducer and the driving power supply, namely impedance matching, frequency matching, power matching, and capacitive reactance matching.
Frequency matching is also very important. This is because the ultrasonic transducer can only work at its resonance frequency, so the drive power supply, horn, and welding die (tool head) should all work at this frequency. Generally speaking, we hope that this difference does not exceed ±0.1khz at most, and it is better if it can be smaller. We strongly recommend that the frequency of the matching welding die (welding head) is lower than the vibrator frequency about 0.1khz (small signal frequency). In other words, if the frequency measured by the small signal of the original vibrator is 14.85 khz, it is most ideal to measure the frequency after connecting the mold to 14.75 khz.
At the same time, it should be considered that after the ultrasonic transducer is connected to the horn and die head, the resonance frequency peak of the system becomes very sharp, that is, the bandwidth is very narrow, the mechanical quality factor is very large, and a little frequency deviation will cause the impedance to be very high. Big increase. Shown in the driving power supply is the power supply (amplitude meter electric power) is very large or overload protection. If the machine is unloaded at exactly this time, it is likely to cause chip misalignment, chip cracks or breakage of the center screw.
Power matching and impedance matching mainly take into account that the ultrasonic welding system is working in gaps, the load changes greatly, there must be sufficient power output during welding, and the minimum amplitude should be controlled when there is no load. Otherwise, as mentioned earlier, if the input is too large at no load, the transducer will be damaged. The power won't go up at full load, and it is useless if the welding is not strong.