Square Tubes Bending Fabrication

How to Bend a Square Tube?

The method of bending square tubes into curved shapes

A. Solid bending

Solid bending, as the name suggests, is a compacted bending process where the inner and outer rollers and the inner and outer walls of the pipe blank are compacted in both directions.

a. The advantages of solid bending are small rebound, accurate forming, and as long as the roller shape is accurate, the R formed at the inner corner is relatively accurate.

b. The disadvantage of solid bending is the stretching/thinning effect. Firstly, actual bending will cause stretching at the bending point, and the stretching effect will shorten the longitudinal length of the bending line; Secondly, the metal at the actual bending point will become thinner due to stretching.

B. Empty bending

Hollow bending is the bending moment formed by the unidirectional contact between the outer roller and the outer wall of the pipe blank, which causes the material to bend. Hollow bending compresses the bending line, causing the bending line to elongate longitudinally. The metal at the bending point accumulates and thickens, which is the compression/thickening effect of hollow bending.

a. The advantage of empty bending is that it can perform edge length bending when solid bending is not possible, such as synchronous bending and finishing of the upper/side edges of square tubes. Empty bending can also bend the inner corner with R<0.2t without causing the pipe wall to break.

b. The disadvantage of air bending is that during synchronous air bending on the upper/side, due to the simultaneous pressure generated by the upper and lower rollers, the forming force is prone to exceed the critical point, causing instability and concave edges, and also affecting the stable operation and forming quality of the unit. This is also a different characteristic when square tube and circular tube are formed by air bending.