SOME EXAMPLES OF ULTRA-SONIC WELDING Coupling shape and positioning makes assembly successful or unsuccessful, even in case of materials that are characterised by good weldability. The geometry of coupling planes must comply with the following basic criteria. A) A reduced initial contact surface to achieve great concentration of energy, which is necessary for rapid melting. B) A sufficient allowance in positioning, so that one of the items to be assembled can vibrate freely compared to the other, and thus create the welding basis. C) A specific area for the melted material to prevent outer burrs. D) If possible, a welding profile that is parallel and/or perpendicular to the vibration vector. E) Prevent the items from being deformed due to moulding. F) The thickness of the surface in contact with the sonotrode must be sufficiently large to prevent the plastics from becoming hollow when ultrasounds are applied. G) It is always appropriate to consult an expert to prevent problems during production operations.