The position of the rollers is at a certain angle to the direction of movement of the straightened product. Two or three larger rollers are the active pressure rollers, which are driven by an electric motor to rotate in the same direction, while several smaller rollers on the other side are the passive pressure rollers, which are rotated by the frictional force of a rotating round rod or pipe. In order to achieve the compression required by rollers for products, these small rollers can adjust their positions forward or backward at the same time or respectively. Generally, the more the number of rollers, the higher the precision of products after straightening. After being bitten by the roller, the product continuously undergoes linear or rotational motion, thus subjecting the product to various forms of compression, bending, flattening, and other deformations, ultimately achieving the purpose of straightening.