Spin Welding

Spin Welding is a process in which two parts are pressed together and while one part is held fixed the other rotates at high speed. The friction between the two parts then generates heat which causes the polymer to melt at the ends. The molten polymer flows out of the weld-zone giving rise to flash. When rotation stops, the weld cools down and solidifies. The duration of the cycle is short which makes it efficient, simple and a fast process. 

The benefit of Spin Welding is that the molten polymer is not exposed to air. This is important for materials that are vulnerable to degradation or oxidation. Such a precautious measure makes for a strong connection or weld.

Spin Welding Process:

The Spin Welding process consists of four different phases; the solid friction phase, the transient phase, the steady-state phase and the cooling phase.

In the solid friction phase, heat is generated as a result of the friction between the two surfaces. This causes the polymer material to heat up until the melting point is reached. The heat generated is dependent on the applied tangential velocity and the pressure.

In the second phase, a thin molten polymer layer is formed which grows as a result of the ongoing heat generation. In this stage heat is generated by viscous dissipation. At first only a thin molten layer exists and consequently the shear-rate and viscous heating contributions are large. As the thickness of the molten layer increases the degree of viscous heating decreases.

Thereafter, (start of third phase) the melting rate equals the outward flow rate (steady state). As soon as this phase has been reached, the thickness of the molten layer is constant. The steady-state is maintained until a certain "melt down depth" has been reached at which point the rotation is stopped.