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Rotation welding offers an effective and efficient way to join thermoplastic materials.
The fusion heat necessary to plasticise the contact surfaces of the corresponding components is generated by a rotational movement that is completed under pressure, resulting in interfacial friction.
The methods associated with this technique fall into two distinct categories: inertia friction welding and pivot pin welding. Both methods are applied at MTV with the help of highly advanced servo drive technologies.
During inertia friction welding, the component to be welded rotates at a specified pressure to generate the necessary welding energy while the bottom component is fixed in place and locked against rotation. The produced energy is converted into heat by friction. Next, the two components are joined under pressure. If the components to be fused possess different lengths, we recommend to spin the shorter component into rotation in order to keep the mass that needs to be moved at a minimum.
In contrast to the aforementioned method, the components welded during pivot pin welding are spun into rotation and pressed together simultaneously and will not stop moving until the welding time has elapsed.
Regardless of the method selected, the precise interplay of rotational speed, time, displacement and pressure along with an exact angle cut-off allows for a smooth and highly efficient process.
Naturally, components that are axially symmetrical such as pipes, flange-pipe connections or injection-moulded and blow-moulded parts are ideally suited for this welding technique. One major advantage of this technique is the fact that it gives the welder a great deal of freedom as to how he wants to join the components because there are no studs or protruding ridges or other types of obstacles that may hinder or impair the welding process.
In theory, all thermoplastic materials as well as all amorphous and semi-crystalline polymers are suitable for rotation welding - similar to ultrasonic welding.
The welding process starts with a start-up phase, during which the surfaces of the components to be joined align with each other. This phase is followed by the main rotation phase. During this phase, the components are partially melted in the joining area by means of pressure and the generated interfacial friction. If necessary, the process also ensures that the component will be positioned at the accurate angle.
While both ultrasonic welding and rotation welding are used to weld together pairs of similar materials, rotation welding offers the following additional advantages.