Hot bar welding
This is a technique, which is mainly used to join thermoplastic films, i.e. materials having a thickness of less than 0.5mm. It is based on the principle that if two thermoplastic films are pressed against a heated metal bar, they will soften and a joint can be made between them. Since the technique relies on the conduction of heat through one of the films, this limits the thickness of material that can be welded. Sometimes two heated bars are employed, one either side of the films, and this has the effect of reducing the welding time.