In my day, Boy Scout manuals described a method for creating a fire by rubbing two pieces of dry wood together. However, this particular Boy Scout was never successful at creating anything more than a sore arm with this technique. I now realize that the problem was that I never achieved speeds of 120 cycles per second in rubbing the two pieces of wood together. Crudely, that, in effect, is the concept behind vibration welding: pressure plus friction combining to create heat. In this case, however, the parts being rubbed together are made of plastic.
This is the principal rotational type of vibration welding. It was created to fill a gap in the market for a mid-size machine that can handle parts up to 305 mm (12 in) in diameter and to accommodate some parts that cannot be made with ordinary vibration welding. With this technique, the two platens rotate in a circular pattern relative to each other as illustrated in Figure 1. Unlike linear vibration welding, which has a non-uniform welding velocity because it must start and stop at each end of its cycle, orbital welding is continuous.