The process of spin welding consists of generating heat by rotational friction to weld thermoplastic parts with circular joints. The spin welding machine applies force axially while rotating one part against its stationary mate. The resulting friction generates heat that melts the parts at the interface. Once rotation stops, the material cools and solidifies, forming a welded assembly. For cases where the parts must be oriented in a particular manner with respect to each other, the welder stops the rotation at a precise angular orientation.
Materials suitable for spin welding are generally the same as those that can be joined by other friction welding processes, such as vibration welding. Semicrystalline thermoplastics are more readily joined using spin welding than ultrasonics. Using compatible polymers, spin welding is capable of making reliable hermetic seals.
Joining of dissimilar polymers is possible using the spin weld process, although it generally produces lower strength weld joints. By designing the weld joint with an undercut, the polymer with the lower melting temperature will flow into the undercut, creating a mechanical union.
Material filler and surface contaminants (e.g. mold release agent) are two factors that will affect consistency and weld repeatability. Spin welding is more tolerant of contaminants than ultrasonic welding. Spin welding is also less affected by hygroscopic polymers, although they may still require special handling for critical applications.