Several techniques are used commonly to reduce profile distortion when air bending with a roll former. These include small-radius forming, false bending, vertical side rolls, and angle side rolls.
When a bend is formed with the air bending process (air bend), the interior of the bending corner can't be reached by either the top roll or the bottom roll, making it difficult to control the part's profile and dimensions. Figure 1 illustrates a typical air bend. The theoretical formed profile is the desired profile. The actual formed profile is the finished part, which was distorted because the top roll couldn't reach the interior corner to hold it in position. The bottom roll flange lifted the section and distorted the profile. Several techniques can reduce such distortion in parts formed by air bending.
The Small-radius Forming Technique
Scoring, grooving, beading, perforating, and interruptive slitting are techniques that can reduce distortion in air bending.
Forming a radius smaller than the metal thickness is a suitable technique for the air bend in Figure 1. Scoring, grooving, beading, perforating, or interruptive slitting weakens the bending track. Scoring is the most commonly used technique. The score depth should not be deeper than one-third the metal thickness in cold roll forming applications. If the score is deeper than one-third the metal thickness, the metal may break at the scored track. In hot roll forming, a grooving track is easy to form and prevents corner cracking.
