3-roll or 4-roll bending machine which to choose?

The choice between a 3-roll and a 4-roll bending machine depends mainly on the type of part to be manufactured and the end finishing requirement.

In a 3-roll machine, the two lower rolls support the plate and the upper roll applies the pressure that produces the curve. The limitation of this configuration is that the plate ends remain flat — uncurved — over a length equivalent to the distance between the upper roll and the exit lower roll. To eliminate those flat ends, the plate must be turned around and reprocessed, or the ends must be preformed in a press before rolling.

A 4-roll machine adds a fourth roll that allows prebending of the plate ends in the same machine, without repositioning. This reduces process time and eliminates the need for a preforming press. The result is a closed cylinder with perfectly curved ends, ready to weld without additional rework.

The 4-roll machine is the right choice when manufacturing shell sections for pressure vessels, tanks, cylinders and any part where the plate end must be perfectly curved. It is also the choice for series production where cycle time is critical.

The 3-roll machine is more economical and perfectly valid for parts where flat ends can be removed later by cutting, or where the welding process covers them. It is also the most frequent choice for structural and architectural parts where end precision is not critical.

CYM Materiales represents Akyapak (Turkey) in Argentina and the region — world-leading manufacturer of rolls and bending machines with more than 60 years of experience and presence in over 100 countries.