Why does the plastic product has burrs after ultrasonic welding?

Sometimes when we weld the plastic products, we will find that the welding edge of the product  have burrs after ultrasonic welding. We will wonder why this happens. We can analyze it from the two main aspects of the machine's own setting and product design, which can be divided into the following six factors:

1) Ultrasonic power is too strong, causing instantaneous overflow during plastic welding

2) Ultrasonic welding time is too long

3) The air pressure (dynamic) is too high

4) The pressure (static) of the ultrasonic welding head is too high

5) The amplitude of the ultrasonic welding head (HORN) is too high.

6) The design of the ultrasonic energy director of plastic products is too outside or too high or thick.

The above six items are the main reasons that cause the product to overflow or burrs after the ultrasonic welding. However, the most critical one is the design of the sixth ultrasonic energy director. Generally, in the ultrasonic welding operation, the air pressure is about In the range of 2~4kg, according to experience, the best ultrasonic energy director is 0.4~0.6m/m times at the bottom; the height is 0.3~0.4mm, and the sharp angle is about 60 degrees. Exceeding this value will lead to ultrasonic welding the increase of time, pressure, machine or upper die power will cause the flash and burrs in items 1 to 6 above.

 

Solutions:

 

1. Reduce air pressure or reduce ultrasonic welding time

2. Reduce the number of machine power stages or use low-power machines

3. Reduce the output amplitude ratio of the ultrasonic horn

4. Use an ultrasonic machine to fine-tune the positioning and fix the downward stroke of the ultrasonic horn 

5. Modify the ultrasonic energy director