The working principle of the Velcro welding machine: 　 When ultrasonic waves act on the thermoplastic plastic contact surface, it will produce tens of thousands of high-frequency vibrations per second. This high-frequency vibration reaches a certain amplitude and transmits the ultrasonic energy to the In the welding zone, because of the large acoustic resistance at the welding zone, that is, the interface between the two weldings, local high temperature will be generated. In addition, due to the poor thermal conductivity of the plastic, it cannot be distributed in time for a while, and it gathers in the welding area, causing the contact surface of the two plastics to melt rapidly, and after a certain pressure is applied, they are merged into one. After the ultrasonic stops, let the pressure continue for a few seconds to make it solidify and shape, so that a strong molecular chain is formed to achieve the purpose of welding, and the welding strength can be close to the strength of the raw material.

The quality of ultrasonic plastic welding depends on three factors: the amplitude of the transducer's welding head, the applied pressure and the welding time. The welding time and welding head pressure can be adjusted, and the amplitude is determined by the transducer and the horn. There is a suitable value for the interaction of these three quantities. When the energy exceeds the suitable value, the melting amount of the plastic is large, and the welded material is easy to deform; if the energy is small, it is not easy to weld firmly, and the applied pressure cannot be too large. The optimal pressure is the product of the side length of the welded part and the optimal pressure per 1mm of the edge.

The method of the Velcro welding machine: 　 

1. Welding method: Ultrasonic vibration transmits the ultrasonic wave to the weldment along with the welding head. Due to the large acoustic resistance at the two weldments, local high temperature is generated and the interface of the weldment is melted. Under a certain pressure, the two weldments can achieve a beautiful, fast and firm welding effect. 

2. Implantation (insertion) method: Nuts or other metals are to be inserted into plastic workpieces. First, the ultrasonic wave is transmitted to the metal, and the metal object is directly embedded in the molded plastic through high-speed vibration, and the plastic is melted at the same time, and the embedding is completed after solidification. 

3. Riveting method: If you want to join metal and plastic or two pieces of plastic with different properties, ultrasonic riveting method can be used to make the weldment not easy to embrittlement, beautiful and strong. 

4. Spot welding method: Use small welding heads to weld two large plastic products at different points, or press the entire row of tooth-shaped welding heads directly on the two plastic workpieces to achieve the effect of spot welding.
5. Forming method: The plastic workpiece is melted and formed instantaneously by ultrasonic waves, and when the plastic is solidified, the metal or other materials of plastic can be firm.
6. Removal method: Utilizing the special design method of the welding head and base, when the plastic workpiece is just shot, it is directly pressed on the plastic branch, and the removal effect is achieved through ultrasonic transmission.