When two surfaces are rubbed together it is possible to generate sufficient heat to cause fusion welding between the materials. This is the basis of friction of welding of plastics. The relative motion between the surfaces may be oscillatory or rotational, although the latter is usually more convenient. They are then brought into rubbing contract and axial pressure applied. When melting has occurred at the interface, rotation is topped but the pressure is maintained to consolidate the weld during cooling of the material. In some cases a boost pressure applied during this latter stage may benefit the strength of the weld. Good weld strengths may be achieved quickly and simply by this welding method.

The important variables in spin welding are the relative surface velocity, pressure, and duration of the rotational phase. By the nature of the process the components usually have a circular cross section.

The disadvantage of spin welding is that it is limited to applications where at least one of the components is symmetrical about its axis.

The low thermal conductivities of thermoplastics means that they are particularly suitable for friction welding and most of them can be joined satisfactorily by this method. In some cases dissimilar plastics can also be joined. but the weld strength are usually less than 50 % of the parent materials.