Common Ultrasonic transducer problems and solutionsDate: 2022-10-08Number: 210
The primary consideration in using a Ultrasonic transducer is matching the input and output terminals, followed by mechanical mounting and fit dimensions. The frequency of the transducer is relatively intuitive. The frequency is measured by the frequency (function) generator, millivolt meter, oscilloscope through the transmission line method, or by network impedance analyzer and other similar instruments measured frequency, generally known as small signal frequency. Corresponding to it is the on-line frequency, that is, the customer will be connected to the transducer by cable to the chassis, power-on after no-load or loaded when the actual working frequency measured.
What if it doesn't work well on a trial basis?
The common problems in the trial are chip cracking, weakness, overloading, electrode firing, electrode cracking, serious fever, strange sound, leakage wave, dislocation of the chip, etc. :
The customer has a problem with the drive power supply or the mold and assembly.
In this case we recommend that customers actively look for the cause or communicate with our technical staff to improve as soon as possible. Even if you do not use our company's products, but improve their own problems is absolutely beneficial and harmless.
L problem with the transducer and the horn.
This is bound to happen, but the chances of discovery are slim.
There are no problems with the products of both parties, but they do not match. This is the most common case, is the customer's drive power supply is good, the transducer is good, the assembly is normal, but the parts do not match. The main parameters causing the mismatch are the frequency and capacitance of the transducer.
Concept and operation of matching?
Let the transducer and drive power, welding mold with a good combination to form a complete ultrasonic equipment, referred to as matching. Since the impact of matching on overall machine performance is critical, the importance of matching can not be overemphasized. The most important factor for matching is the capacitance of the transducer, followed by the frequency of the transducer.
It should be emphasized that the Ultrasonic transducer is not an energy generator per se, it is merely an energy converter. It is the conversion of electrical energy into acoustic energy (mechanical energy) , in the input (driving power) , the output (amplifier, mold) well-matched premise, it can convert (output) a great deal of energy.
Input matching refers to the matching of the transducer and the driving power, if the output matching is good and the input matching is not good, then the performance of the transducer is weak, weak welding. If the output matching is not good and the input matching is good, then the transducer will be overloaded, resulting in chip dislocation crack, broken, screw broken, aluminum crack or burning box power tube. For example, just like a car slamming the accelerator in neutral, the engine is liable to break down.
The matching of transducer and drive power supply mainly has 4 aspects, namely impedance matching, frequency matching, power matching, capacitance and reactance matching. One of the most important is the tolerance and frequency. As mentioned earlier, because the ceramic plate is an insulator, you can almost understand that the transducer is not energized, it is just the equivalent of a capacitor. To make the transducer work, it is actually through the drive circuit to apply a high AC voltage to it, so that the transducer capacitor charge and discharge. Under the action of alternating electric field, the piezoelectric ceramic plate makes synchronous expansion and contraction deformation, which forms the longitudinal vibration of the whole transducer and drives the vibration of the horn and the die. Therefore, if the capacitance match is not good, the light is weak transducer, welding is not strong; heavy transducer heating serious, burning electrode plate, burning power supply of high-power tube. Our transducer products come with a product performance parameter table that gives the capacitance and frequency of each transducer. The driving power supply should adjust the high-voltage transformer according to the capacity of the transducer and match the parameters of the capacitor board, the honeycomb coil, the 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. Moreover, as the work goes on, the temperature of the transducer will rise, resulting in an increase in the capacitance and the variation may exceed 50% , if the capacitance can not be effectively matched off, it will result in a large current and voltage phase difference in the circuit, low power factor, high virtual work. Look at the current
Very large, but the transducer is weak, easy to heat, and the power supply of the power device is also easy to heat damage. It is likely that the electrode plate (ear) of the transducer will crack or burn off as a result.
Frequency matching is also important. First of all, because the ultrasonic transducer can only work at its resonant frequency point, so the drive power, amplifier, welding mold (tool head) should be working at this frequency. In general, we want this difference to be no more than ± 0.1 khz, preferably smaller. We strongly recommend that you match the welding mold -LRB-welding -RRB-ead) frequency is lower than the vibrator frequency 0.1 khz or so (small signal frequency) . In other words, if the original oscillator small signal measurement frequency is 14.85 khz, then connected to the mold and then measured frequency is 14.75 khz is the most ideal. It should also be taken into account that when the Ultrasonic transducer is connected to the amplifier and the die head, the resonant frequency peaks of the system become very sharp, that is, the bandwidth is very narrow and the mechanical quality factor is very large, frequency offset at any point will result in a large increase in impedance. In the driving power supply is the power supply (amplitude meter power) is very large or overload protection. If just at this time is no-load conditioner, it is likely to cause chip dislocation, chip cracks or broken central screw.
Power matching and impedance matching mainly take into account that the Ultrasonic welding system is a gap work, the load changes greatly, welding to have enough power output, when no-load to control at the minimum amplitude. Otherwise, as mentioned earlier, a large input at no load will damage the transducer. It is useless if the power does not go up when the load is full.
the components of the assembly notice
The main parts of the ultrasonic vibration system, such as transducer, amplifier, tool head and so on, are connected by the center bolt. 1, check the contact surface should be flat and smooth without scars, if there are scars, with zero above the metallographic sandpaper gently polished. It is required that the defects can be smoothed without destroying the flatness of the contact surface. 2. Clean the screws, holes and contact surfaces with a volatile non-corrosive detergent. 3. Thoroughly clean screws, holes and contact surfaces. 4. All connecting screw holes shall be perpendicular to the contact surface. 5. Apply a thin layer of silicone (or butter and vaseline) to the contact surface before tightening. Be careful not to apply silicone to the connecting screws and holes. Tighten both parts carefully. According to the different specifications of connecting screws, control the appropriate tightening torque. When possible, screw it properly tight. If you re-release the joint should not see any scars. 8. Touch the vibration system by hand, the amplitude is even, no strange sound, no local serious fever. 9, after working for a period of time to re-open the joint should be no oxidation or ablation marks, otherwise it means that the contact here is not good, where the loss of ultrasonic energy is serious.
the use of the transducer temperature
There are three main reasons for the heat generated when the transducer is in use. One is that the welded workpiece will heat or be ultrasonic treatment, the material will heat, or mold (tool head) , horn long-term work will heat, these heat will be transferred to the transducer.
The other is the power loss of the transducer itself. If you can't get 100% energy efficiency, the energy you lose must be converted into heat. Temperature rise will lead to the change of transducer parameters, and gradually shift the best matching state. More seriously, temperature rise will lead to the deterioration of piezoelectric ceramic chip performance. This in turn causes the transducer to work worse and heat up faster, a vicious cycle. So we must give the transducer good cooling conditions, generally is room temperature air-cooled; if necessary, can also be used air-cooled. Under normal conditions, the temperature rise caused by these two points is also normal, under normal cooling conditions, there will be no major problems.
In practice, we found that there is a third reason, is that the customer in the use of the transducer and drive power supply matching to the best working state, which caused the heat is very large, and is not controlled, can have serious consequences. At the same time, high temperature, the mechanical strength of aluminum on a sharp decline in the role of high-power, cracking is inevitable. Obviously is the good thing, because uses improperly causes the damage, is really too is a pity. Our company has suffered a great loss, but yours is even greater. Therefore, we hope to work together with your company to improve the level of application technology.
According to the domestic and foreign experience, the temperature of the transducer must not exceed 85 °C at any time.