Tube Bending Processes

Press bending
In Press bending, a die in the shape of the bend is pressed into the inner radius of the bend, forcing the pipe to fit the shape of the bend. Because the pipe is not supported internally, there is some deformation of the shape of the pipe, giving an ovular cross section. This process is used in steel and copper tube bending where a consistent cross section of the pipe is not required. Typical tooling for Press bending would include a bend punch, and two support or wing dies.

Rotary draw benders
Rotary draw benders are precise in that they bend using tooling or "die sets" which have a constant center line radius (CLR). The die set consists of four components: The bend die creates the shape to which the material will be bent. The clamp die secures the tube against the bend die ahead of the point of tangency, holding the material secure throughout the required degrees of bend rotation. The pressure/reaction die holds the material into the bend die while traveling the length of the bend. The collet set is used to maintain or position the rotation of the tube throughout the tube fabrication and bending operation. Rotary draw benders can be programmable to store multiple bend jobs with varying degrees of bends, including multiple radiuses and 2D and 3D shapes. Rotary draw benders are the most popular machines for use in bending tube, pipe and solids for applications like handrails, frames, motor vehicle roll cages, handles, lines and much more. Typical tooling sets are unique to the tube diameter, required center line radius (CLR), and degrees of bend required, and would include a bend die, clamp die, reaction/pressure die, and a collet.

Mandrel benders
Mandrel bending allows a tube to be bent to a tight radius, while maintaining much of the integrity of the original tube cross section geometry. Typically, a mandrel is needed when bending thin wall tubing to a radius much tighter than the material can bend without collapsing or distorting. The word mandrel refers to the part of the tooling set which is inserted into the tube and remains inside the tube during the bend process. This internal mandrel helps to support the shape of the wall when bending. Many different configurations of mandrel exist; however, the plug mandrel and ball mandrel are two of the more common. In conjunction with a mandrel assembly, a wiper die is often required to support the material on the outside of the tube where the work is being performed. This tooling is used in conjunction with a bend die, clamp die, reaction/pressure die, and collet, and is most often performed on a rotary draw bender. In situations where the center line radius (CLR) is less than the tube diameter, or in cases of some materials, mandrel bending will need to be combined with boost bending to ensure the integrity of the material and bend. Boost or push bending requires some type of assistance to the forward movement of the tube during the actual bend.

Roll bending
During the roll bending process the pipe, extrusion, or solid is passed through a series of rollers (typically 3) that apply pressure to the work piece gradually changing the bend radius. This method of steel or copper tube bending causes very little deformation in the cross section of the pipe. This process is suited to producing coils as well as long gentle bends, and can often be used in conjunction with other tooling on multi radius CNC controlled benders. If you have questions regarding the tube bending process, or any of our tube fabrication products and services, please contact us today.