Precautions for the Use of the Ultrasonic Transducer
The main consideration when using an ultrasonic transducer is the matching with the input and output ends, followed by mechanical installation and matching dimensions. The ultrasonic transducer frequency is relatively intuitive. The frequency refers to the frequency measured by the transmission line method with a frequency (function) generator, millivoltmeter, oscilloscope, etc., or the frequency measured with a similar instrument such as a network impedance analyzer. It is commonly referred to as small signal frequency. The customer connects the ultrasonic transducer to the drive power supply through the cable, and the actual working frequency can be measured when no load or on load is energized. Because the customer matching circuit varies, the same ultrasonic transducer in different drive power supply performance of the frequency is different, such frequency can not be used as the basis for discussion.
Ⅰ. Problems that tend to occur when using ultrasonic transducers
Common problems when using the ultrasonic transducer are chip cracking, weakness, overload, electrode ignition, electrode chip cracking, heat generation, wave leakage, and chip dislocation. The causes of such problems can be classified into three categories. First is that there is a problem with the customer's drive power supply or mold and assembly; second is that there is a problem with the transducer and horn; and the third is that there is no problem with the products of both parties, but they do not match.
Ⅱ. Precautions for assembly of each part of ultrasonic transducer
The main parts of the ultrasonic vibration system, such as the transducer, amplitude rod and tool head, are connected by a central bolt.
1. Check the ultrasonic transducer in biomedical application. Its contact surface should be smooth and without scratches. If there are scars, lightly sand it with metallographic sandpaper above zero. It is required to be able to smooth the defects without destroying the flatness of the contact surface.
2. Clean screws, screw holes and contact surfaces with a volatile, non-corrosive cleaner.
3. Clean screws, screw holes and contact surfaces thoroughly.
4. All connection screw holes should be perpendicular to the contact surface.
5. Before tightening, apply a thin layer of butter or vaseline on the contact surface, taking care not to apply it to the connecting screws and screw holes.
6. Carefully tighten the two parts. According to the different specifications of the connecting screws and types of ultrasonic transducers, control the appropriate tightening force. Under appropriate circumstances, the screws should be tightened a little bit tighter.
7. If the bonding surface is loosened again, no injury should be visible.
8. Feel the vibration system by hand, the amplitude is even, no strange sound, no partial serious heat.
9. After the ultrasonic transducer has been working for a period of time, loosen it again, and there should be no traces of oxidation or ablation on the joint surface. Otherwise, it means that the contact here is not good, and the ultrasonic energy is lost seriously here.
Ⅲ. Operating temperature of ultrasonic transducer
Ultrasonic transducers will generate heat when used, which is mainly caused by three reasons. The first is that the workpiece to be welded will heat up or the material processed by ultrasonic will heat up, or the mold (tool head) and the horn will heat up for a long time, and these heat will be transferred to the transducer. The second is the power loss of the transducer itself. Since 100% energy conversion efficiency cannot be achieved, the part of energy lost must be converted into heat. Temperature rise will lead to changes in ultrasonic transducer parameters, gradually deviating from the best match. And more seriously, it will lead to the deterioration of the performance of the piezoelectric ceramic wafer. Therefore, we must provide good cooling conditions for the ultrasonic transducer in biomedical application, which are generally air-cooled at room temperature. If necessary, cold air cooling can also be used. Under normal conditions, the temperature rise caused by these two points is also normal. Under normal cooling conditions, there will be no severe problems.