1) Misunderstanding in the principle of welding
There are quite a few people who have been engaged in ultrasonic welding for many years. There is a misunderstanding about the transmission of ultrasonic energy. It is considered that the sound wave is welded on the contact surface. In fact, this is a misunderstanding. The principle of true ultrasonic welding is: The transducer converts electrical energy into After the machine, the sound is transmitted through the material molecules of the workpiece. The sound resistance of the sound wave in the solid is much smaller than that in the air. When the sound wave passes through the joint of the workpiece, the sound resistance in the gap is large, and the heat energy generated is quite large. First, the tolerance of the workpiece is reached, and a certain pressure is applied to weld the joint. The other parts of the workpiece are not welded due to low thermal resistance. The principle is similar to Ohm's law in electrotechnics.
2) Mistakes in workpiece materials:
Ultrasonic welding machines are also required for the material of the workpiece to be welded. Not all materials can be welded. Some people understand that any material can be welded. This is a big misunderstanding. Some materials can be welded better. Some are basically capable of phase fusion, some are not phase fusion. The melting point of the same material is the same, from the principle that it can be welded, but when the melting point of the workpiece to be welded is greater than 350 ° C, it is not suitable for ultrasonic welding. Because ultrasonic is the instant melting of the workpiece molecules, the judgment is based on 3 seconds, can not be welded well, you should choose other welding processes. Such as hot plate welding, etc. Generally speaking, ABS material is the easiest to weld, nylon is the most difficult Spliced.
3) Process misunderstanding of ultrasonic welding of workpieces Ultrasonic energy is instantaneously erupted, the welds should be in points or lines, and the distance of transmission must conform to the ultrasonic welding method. Some people think that as long as it is a plastic material, it can be welded well regardless of the joint surface. This is also a misunderstanding. When the instantaneous energy is generated, the larger the joint area, the more severe the energy dispersion, the worse the welding effect, or even the welding. In addition, the ultrasonic wave is longitudinally transmitted, and the energy loss is proportional to the distance, long distance. Welding should be controlled within 6 cm. The welding line should be controlled between 30----80 filaments. The arm thickness of the workpiece should not be less than 2 mm, otherwise it will not be welded well, especially for products requiring airtightness.