The typical profile for an ultrasonic weld serves two functions:It is designed as a tongue and groove joint in order to:

• facilitate the lay-up of work
• guide the two halves of the workpiece precisely during the processing operation

The energy director integrated in the contact zone acts as an energy concentrator, and at the same time it supplies the necessary molten mass for an optimum joint.

The weld profile is adapted to the particular case of application, i.e. there are several variations.

Machine set-up parameters such as welding force and amplitude are calculated to enable the top half of the workpiece to move in phase with the horn.

The bottom half lies in the fixture and is passive. This brings about a phase shift in the movement between the two halves of the workpiece, resulting in friction at the point of contact.

This highly intensive ultrasonic oscillation causes the point of contact between the two halves of the workpiece to melt instantly. The simultaneous input of force from the press, which lasts longer than the ultrasonic pulse, holds the welding halves of the workpiece until the molten plastic solidifies.

Rivet joints are used among other things to join injection moulded plastic parts to parts made of a different material. Moulded spigots on the injection moulded part penetrate the foreign part that is to be riveted to it. The section projecting above the foreign part is then deformed into a rivet head using a pre-formed horn. The cavity in the horn tip must be designed to take up the volume of the displaced material. The amplitude of the horn must be set to result in complete decoupling between the workpiece and the horn surface.

This results in the generation of direct frictional heat at the point of contact between the plastic part and the metallic surface of the horn. Instant plastification takes place at this point. The resulting rivet head is given enough time to harden under the action of force from the press.

Multiple tools are often used for riveting operations in order to rivet parts at various points simultaneously.

Spot welding is called for, for example, wherever large thermoplastic parts cannot be loaded under a welding press for practical reasons.

In these cases the welding head is taken to the object to be welded. The weld is then performed with a welding gun either manually or by robot. The advantage of ultrasonic spot welding is that the parts do not require any special preparations at their welding points (an energy director is not essential).

Even deep-drawn parts can thus be processed without difficulty. The ultrasonic tool is designed to generate a relatively high amplitude.

The tip of the horn is specially formed so that the advancing tip penetrates the half to be welded and the displaced material is caught and positively shaped in an outer ring.

Preformed openings to be firmly plugged by a threaded insert pin, connector or the like.

The sontrode makes contact with the foreign part and sets it vibrating, the high intensity of its movement causing the plastic body to plasticize at the point of contact.

The penetrating movement executed simultaneously by the welding press displaces the now ductile material into the specially provided backtapers and cavities in the inserted part.

When the displaced material solidifies, the embedded part remains firmly trapped. It is thus invested with high tensile and torsional strength.