Assembly
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Ultrasonic Welding
Did you know?
Ultrasonic welding is the most common assembly method for
thermoplastic parts. The process is fast and effective at
providing a strong, reliable bond.
How does it work?
An ultrasonic welder transmits energy through a metal “horn”
to the plastics being bonded (see figure
5). Only one of the two plastics
comes into contact with the horn. Ultrasonic energy causes
the contact area to vibrate creating a consistently quick,
tight weld.
The plastic melts only at the points where the horn is positioned
over the plastic. Welding is either “Near Field”
or “Far Field”:
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- Near Field – where the horn is within 0.25 inches
of the weld. This is optimal as most of the energy is
transmitted this way.
- Far
Field – where the horn is more than 0.25 inches
away from the weld.
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Key Factors:
The key factors in a good weld are:
- Joint design
- Material compatibility – different materials can be bonded but compatibility must be taken into account
- Part design – this includes joint design, wall thickness, size of part and bonding plane
- Horn and fixture designs
- Near or Far Field
- Power of welder, weld and hold time and clamp pressure
- Joint cleanliness
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