Ultrasonic welding is a very expensive approach for the prototype project. Large companies can afford to put aside an expensive welder for trial work. Then their R&D staff have to design a horn and jig to concentrate the wave onto the joined surface ie the sonic horn is designed to concentrate the wave and the jig is designed to reflect the wave (like a mirror) back into the joined part and actually combine the initial and the reflected waves at the depth distance of the joint where the ultrasonic energy is focused and heats up the material to its melting point. If you try to use any old jig and horn, you will simply pump lots of ultrasonic energy into the whole part and simply warm one or both pieces up, but without concentrating the energy, no melting will take place.
.
This is excellent technology to seal electronics, no mess, no excess glues, the product is sealed from repair by unauthorized tinkering. It's an expensive method, but cheap in volume. Tuning an engineered horn (one specifically designed for the housing) still needs to be done by a floor technician with experience. ie often you still need to make several adjustments to the welding machine, even though YOU know the jig and horn are supposed to weld. Often, even an experienced tech will burn the surface of the item (smooth out or melt the exterior) until he gets the welders settings and proper pressures to weld at the depth of the joint.
