Roll-formed parts are subject to end distortion when the parts are cut at the end of the roll-forming line. Understanding the forces that contribute to end distortion is the first step to balancing the forces and eliminating end distortion.
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End distortion is a birthmark caused by the roll forming process. Roll forming—a process in which a flat strip is bent continuously and progressively in the transverse direction by tandem sets of roll tooling—induces residual stresses in compression on the inner surface, residual stresses in tension on the outer surface, and residual moments in the cross section. Cutting the formed part releases the residual stresses and moments, which can result in distortion at both ends of the part. Understanding the causes of end distortion can help fabricators prevent and correct these types of defects in roll formed parts.
