Welding The basic principle of ultrasonic welding
Step 1 - Parts in fixture
The two thermoplastic parts to be assembled are placed together, one on top of the other, in a supportive nest called a fixture.

Step 2 - Horn contact
A titanium/steel or aluminum component called a horn is brought into contact with the upper plastic part.

Step 3 - Pressure applied
A controlled pressure is applied to the parts, clamping them together against the fixture.

Step 4 - Weld time

Step 5 - Hold time
The clamping force is maintained for a predetermined amount of time to allow the parts to fuse as the melted plastic cools and solidifies. This is known as hold time. (Note: Improved joint strength and hermeticity may be achieved by applying a higher force during the hold time. This is accomplished using dual pressure.)

Step 6 - Horn retracts
Once the melted plastic has solidified, the clamping force is removed and the horn is retracted. The two plastic parts are now joined as if molded together and are removed from the fixture as one part.