1. Conducting energy through vibration.
2. The heat energy directly contacts the plastic surface.
These two points are the two conditions that will occur when the ultrasonic spot welder machine is working, so it is easy to burn the welding elements. For plastic parts with thin wall thickness, it is easy to crack. These are unavoidable.

There are also some other reasons that can avoid cracks or fractures. For example, sometimes when the power is not enough, it is mostly through long-term welding to accumulate heat to make up for the lack of power. In this way, the heat will act on the surface of plastic parts for a long time, causing products to burn, and these things can be completely avoided.

Resolvent:
1. Reduce the time of welding, that is, reduce the action time of heat on plastic parts.
2. Start the vibration in advance.
3. Reduce the pressure.
4. Reduce the delay time (start vibration earlier).
5. Reference media coverage (such as PE bag).
6. Add R angle to the right angle of the easily broken product.
7. Surface treatment (hardening or chrome plating) of die and fixture.
8. The number of machine sections is reduced or the expansion ratio of upper mold is reduced.

9. Fixtures should be made into buffered, easily cracked or broken products. Such as soft resin or covered cork plug (this item does not affect the welding strength).