Tube Bending methods

To avoid collapse or wrinkling, a mandrel is often inserted inside the tube during bending, especially for thin-walled materials. The wiper die, typically made from a softer alloy like aluminum or bronze, helps maintain a smooth surface by preventing creases as the tube slides past the tooling.

Several common methods are used:

Press Bending
This is one of the simplest methods. A die is pressed into the pipe, forcing it into a bend. Since the tube lacks internal support, its cross-section can become slightly ovalized. This method is suitable for applications where a perfect cross-section is not critical.

Rotary Draw Bending (RDB)
This is a precise method that uses a set of dies to draw the tube around a fixed form, creating a consistent bend radius. CNC-controlled rotary draw benders can store multiple programs for complex, multi-bend parts. It is widely used for high-quality bends in applications like handrails, automotive frames, and fluid lines. Tooling often includes a mandrel and a wiper die to prevent wrinkling and ovalization.

Roll Bending
In this process, the tube is passed through a series of three rollers that gradually apply pressure to create a curve. This method is ideal for forming large, gentle radii or coils, such as those used in trusses, and causes minimal deformation to the tube's cross-section.

Three-Roll Push Bending
A more flexible variation, this process uses three rolls to create freeform bends, including complex shapes with multiple curves. The bending radius is determined by the position of the forming roll. While not as precise as rotary draw bending, it offers greater geometric flexibility from a single tool set.

The choice of method depends on the desired bend quality, complexity, and the specific application requirements.