Ultrasonic welding is to convert 50 / 60 Hz current into 15, 20, 30 or 40 kHz power by ultrasonic generator. The converted high-frequency electric energy is converted into the mechanical motion of the same frequency again through the transducer, and then the mechanical movement is transmitted to the horn through a set of horn device which can change the amplitude. The vibration energy received by the horn is transferred to the joint of the workpiece to be welded. In this area, the vibration energy is converted into heat energy by friction, and the plastic is melted. Ultrasonic can be used not only to weld hard thermoplastic plastics, but also to process fabrics and films. Heat energy comes from the reciprocating movement of a workpiece on another surface with a certain displacement or amplitude under a certain pressure. Once the expected welding degree is reached, the vibration will stop, and at the same time, there will still be a certain pressure applied to the two workpieces to cool and solidify the just welded parts, thus forming a close combination.

Ultrasonic problem one: abnormal overload of ultrasonic current
When the generator sends out an overload alarm, check as follows:
1. Sometimes the no-load test is normal, but it can not work normally. It may be that the internal changes of the welding head and other sound energy components lead to poor sound energy transmission. Here is a relatively simple judgment method: hand touch method. The amplitude of the normal working welding head or horn surface is very uniform, and the hand feels smooth like velvet. When the sound energy transmission is not smooth, there will be bubbles or burr when the sound energy transmission is not smooth. At this time, the elimination method should be used to eliminate the defective parts. When the generator is abnormal, the same situation can be produced, because normally, the input waveform of the transducer should be smooth sine wave. This phenomenon can also occur when there are spikes or abnormal waveforms on the sine wave. In this case, another whole branch acoustic energy element can be used to distinguish.
2. Ultrasonic no-load test, if the working current is normal, it may be that the ultrasonic welding head contacts the object that should not be contacted or the parameter adjustment between the ultrasonic welding head and the welding base is faulty.
3. When the ultrasonic no-load test is abnormal, first observe whether there are cracks in the ultrasonic mold and whether the installation is firm. Then remove the welding head and then conduct the no-load test to exclude whether there is a problem with the ultrasonic transducer + ultrasonic horn, and eliminate step by step. After eliminating the possibility of transducer + horn failure, the new welding head shall be replaced to judge.
Ultrasonic problem 2: abnormal heating of ultrasonic mold
When the ultrasonic mold is working, there will be a certain heating phenomenon, which is caused by the mechanical energy loss of the material itself and the heat conduction of ultrasonic objects. Whether the heating of ultrasonic mold is normal or not is judged as: when the ultrasonic mold is not loaded (i.e. not contacting the workpiece), the ultrasonic wave is continuously emitted for more than half an hour, and the temperature should not exceed 50-70 ºC. If the heat is damaged, it is proved that the ultrasonic mold has been damaged or the material is unqualified and needs to be replaced; if the mold temperature is too high, it is usually accompanied by abnormal high ultrasonic current;
Ultrasonic problem three: ultrasonic mold howling abnormal
When the ultrasonic mold screams, the following reasons should be analyzed:
1. Whether the ultrasonic mold is in contact with the object that should not be contacted;
2. Whether the screw of ultrasonic welding head is loose;
3. Whether there are cracks in ultrasonic mold;