What are the types of Ultrasonic transducer?Date: 2022-10-07Number: 182
The Ultrasonic transducer is a type of energy conversion device that converts electrical power into mechanical power (i.e. , ultrasonic) and transmits it. It consumes a very small part of the power (less than 10%) . Therefore, the first consideration in adopting a Ultrasonic transducer is also matching the input and output terminals, followed by mechanical mounting and assembly dimensions.
Ultrasonic transducer classification:
2. Reverse Horn
3. Steel back cover type
4. Aluminum plate in the middle
Generally used in ultrasonic plastic welding machine, ultrasonic cutting knife, ultrasonic metal welding machine, ultrasonic cleaning machine, ultrasonic sonochemical equipment.
The Ultrasonic transducer can vibrate periodically under suitable electric field excitation, the amplitude of which is usually about 10μm. It is not enough to realize welding and machining process immediately. The amplitude of the ultrasonic wave can be changed in a very large range after connecting the horn according to the reasonable design, as long as the material strength is sufficient and the amplitude can exceed 100μm.
Due to the different processing methods, the work of the transducer can be divided into continuous work (such as lace machine, CD machine, cleaning machine, zipper machine) and pulse operation (such as Plastic Welder) , different working states require different types of transducers. Usually, the continuous operation of basic no discontinuous time, but the working voltage is not big, pulse work is intermittent, there are discontinuous, but the instantaneous current is very large. On average, the power in both states is very large.
The first consideration in Ultrasonic transducer is also matching the input and output terminals, followed by mechanical mounting and assembly dimensions. The frequency of the transducer is relatively straightforward. The frequency is measured by the frequency (function) generator, millivolt meter, oscilloscope, such as through the transmission line method, or by network impedance analyzer, such as the frequency measured by similar instruments. Usually referred to as a small signal frequency. And it matches is on the machine frequency, that is, the customer will be connected to the box according to the cable, power after no-load or loaded when the specific working frequency measured. Because the customer matching circuit is different, the same transducer in the respective drive power supply (box) of the frequency is different, so the frequency can not become an important basis for AC discussion.
To make the transducer and drive power supply, mold to maintain a good fit to produce a complete ultrasonic equipment can be called matching. Given that the impact of matching on overall machine performance is decisive, the need for matching can not be overemphasized. The primary consideration for matching is the capacitance of the transducer, followed by the frequency of the transducer.
The matching of transducer and driving power mainly includes 4 fields, i. e. impedance matching, frequency matching, power matching and capacitance-impedance matching. The most important thing in this is to accommodate reactance and frequency. As mentioned above, because the ceramic plate is an insulator, you can even say that the transducer is not electrified, but is equivalent to a capacitor. What makes the transducers work is, in fact, that the drive circuit exerts pressure on them by alternating high voltages to charge and discharge the transducers' capacitors. Under the influence of alternating electric field, the piezoelectric ceramic plates expand and contract at the same time, which forms the longitudinal vibration of the whole transducer, and then drives the vibration of the horn and the die. Therefore, if the capacitance match is not good, light is weak transducer, welding is not firm; heavy is the transducer heating obvious, burning electrode plate, burning power supply of high-power tube. Our own transducer equipment comes with a product characteristic parameter table that presents the capacitance and frequency of each transducer. The driving power supply must adjust the high-voltage transformer according to the capacity of the transducer, and match the parameters of the capacitor board, peaking coil, frequency modulation coil, etc. . Because of the sensitivity of inductance and capacitance, the power amplifier board, choke coil and other peripheral circuits also affect the matching. But as things go on, the temperature of the transducer will rise, so will the capacitance, and the change may exceed 50% , if the capacitance can not be matched more effectively, it is easy to appear in the loop current and voltage phase difference is very large, active power is relatively low, high virtual work. Look at the current is very large, but the transducer is weak, easy to heat, and the power supply of the device is also very easy to heat damage. Usually the transducer electrode plate (ear) vibration break or burn is likely to be the result.
Frequency matching is also crucial. This is mainly because the ultrasonic transducer only operates at its resonant frequency point, so drive power, horn, Mold (tool head) need to operate at such a frequency. In general, this difference should not exceed a maximum of ± 0.1 khz, preferably smaller. We strongly require the matching mold -LRB-welding -RRB-ead) frequency less than the vibrator frequency 0.1 khz or lower (small signal frequency) . In other words, if the small signal of the original oscillator is measured at a frequency of 14.85 khz, then it is ideal to measure the frequency of 14.75 khz after connecting the die. At the same time, it should be fully considered that when the Ultrasonic transducer is connected to the horn and the die head, the resonant frequency peak of the system becomes sharper and sharper, that is, the bandwidth is too narrow, and the quality of the mechanical equipment is very important, a small shift in frequency will result in a very large increase in impedance. Mainly reflected in the driving power supply is the power supply (amplitude meter power) is very large or overload protection. If it happens at this time is no-load conditioner, it is likely to cause the chip displacement, chip fracture or the center of the screw broken.
The purpose of power and impedance matching is to take full account of the fact that the Ultrasonic welding operating system operates in a gap mode, the load varies greatly, a certain amount of power output is required during welding, and the minimum amplitude should be maintained during no-load operation. Otherwise, as mentioned above, if the input is very large at no load, the transducer will be destroyed. It doesn't work when it's full.