Metallic materials when external force exceeds the yield limit its materials, will produce permanent plastic deformation, which is the basic principle of the tube bending. Bending the tube, the outer wall due to its stretching and thinning of the medial compression due to thickening, since the result of stretching and compression, and in the bending process, the tube cross-section has changed, a change in a circular into the trend of the ellipse.

Tube bending method is divided into two kinds of cold bending and bending, cold is at room temperature with a direct elbow bending machine, bending sucked the curved portion of the tube is heated to a certain temperature, and then the mechanical (bending pipe machine) or manually elbow. Cold-formed metal does not destroy the original nature, does not produce thermal deformation. But cold-formed elbows need to consume more power, and the rebound and residual stress has a more significant increase, but not bending radius of curvature of cold-formed small sharp turn heads. Bending it can not be compared with a cold-formed adaptability.

Bending and welding in accordance with the order, bending process can also be divided into “first bending and welding” and “after the first weld bend” in two different bending processes. The so-called “first bending and welding,” is based on various parameters of the tube pipe or rod-like parts processing diagram provided, the first tube bending. And then in the SAMS or SAMS platform for positioning the tube flange connection accessories, the welding work. Determine the length of straight pipe cutting machining parts according to drawing or sample tube rods, the error when considering the elbow, cutting the length of the process to put the general allowance. The “first weld bend” is based on the length of the tube draw the line pipe size computer output value of the parts diagram, the relative angle flange screw K, flange screw angle and the NC program and a series of processing data, using no margin under material, first on the platform or SAMS machine positioned straight pipe flanges, welding, and then bending work.