Due to the different structure of various equipment, so the universal shaft length requirements are not the same. Designers ​sometimes very vexed, installation distance is too short afraid of universal shaft can not be made, installation distance is too long, and will worry about the concentricity of the whole shaft.

The friction heat generated by the friction between thermoplastic plastics is melted on the friction surface, and then the pressure is pressed, and the method of cooling under pressure is called friction welding. This method is most suitable for rotating body parts. Similar to friction welding of metals, one piece is fixed while the other rotates and pressure is applied.