1. Both weldment materials shall be fusible. Some Weldments of different materials cannot be welded. Theoretically, the same material can be welded, but there is a problem, that is, when the melting point of the weldment is higher than 350 ℃, ultrasonic welding is not applicable.
2. The thermal resistance of the weldment shall be higher than its melting point. When ultrasonic wave propagates through weldment in solid, it belongs to propagation in air. The acoustic impedance of ultrasonic wave propagating in air is greater than that in solid. The greater the acoustic resistance, the higher the heat generated. Therefore, the temperature of the parts in contact between the two weldments is high, and the melting point is reached first. When propagating inside the weldment, the acoustic resistance is small, the temperature is relatively low, and the melting point will not be reached.
3. Required connection area and distance. The welding contact area between two weldments shall meet the welding requirements and shall not be too large or too small. Too much contact will lead to scattered welding energy, insufficient welding strength, or even impossible to weld together. The contact is too small, the welding is not firm, and it is easy to disconnect. The longer the distance, the greater the energy loss. Therefore, the welding distance should be controlled.
4. The importance of ultrasonic mold the manufacture of ultrasonic welding head mold can only be completed through a set of strict procedures, which is impossible for ordinary small workshops. Therefore, do not buy ultrasonic mold from small manufacturers, which will make you unable to weld well.

5. In order to keep the output power of the ultrasonic medical welding machine constant, it is necessary to ensure that the output power of the ultrasonic plastic welding machine is constant, not too high or too low, otherwise it will have adverse effects on the weldment.