Ultrasonic Assembly
Ultrasonic assembly, one of the most widely used joining techniques for thermoplastics, makes permanent, aesthetically pleasing joints. Four common ultrasonic assembly techniques are welding, staking, spot welding and ultrasonic inserts. They use high frequency mechanical vibration to melt mating surfaces. An ultrasonic plastic assembly system converts standard electrical energy from 50/60 Hz to 20/40 KHz and then into mechanical vibratory energy. A 40 KHZ machine produces one-half the amplitude of a 20-KHz unit, allowing for a more gentle action.
The ultrasonic assembly techniques of welding, staking and ultrasonic inserts can’t be used in large parts or extruded sheets, whereas ultrasonic spot welding can be used in these parts.
Ultrasonic Spot Welding:
Requiring no preformed holes or energy directors, ultrasonic spot welding
joins two layers of thermoplastic resins with similar melting temperatures
in a single location, forming a permanent bond.
In ultrasonic spot welding, the pilot tip melts through the first surface.
As the tip penetrates the second or bottom surface, displaced molten plastic
flows between the two surfaces, forming a bond (see figure 1).
Generally used for large parts or sheets, ultrasonic spot welding can be done with a portable, hand-held device and power supply.
Figure 1 - Ultrasonic spot welding
