The spiral welded pipe is formed by a spiral former, which can be divided into two types: up-rolling and down-rolling. There are three basic forms of the former structure of the spiral welded pipe:
(1) Sleeve type spiral former. Only suitable for the forming of small diameter welded pipes. It is low cost and easy to operate.
(2) Roller spiral forming device. The roll former is made according to the working principle of the three-roll bending machine. The contact surface between the former and the strip steel is rolling friction, with low resistance, long tool life, and almost no scratches on the surface of the product.
(3) Mandrel screw former. This former is suitable for the forming of small diameter, thin-walled high-quality spiral welded pipes. However, the inner surface of the steel pipe may be scratched due to friction.
