Three-Roller spinning principle：Cylindrical deformation thinning spinning refers to the thin-walled long cylindrical parts produced by pressing of the spinning rollers on the tube blank which rotates simultaneously with the mandrel and moves along the axis of the tube blank. This spinning process always follows the principle that the volume of metal material remains unchange. According to the direction of motion, it can be divided into two spinning modes: positive spinning in which the direction of material flow coincides with that of the roller; and reverse spinning in which the direction of material flow is opposite to that of the roller.